Zinc supplements for treating thalassaemia and sickle

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Zinc supplements for treating thalassaemia and sickle cell disease Article in Cochrane database of systematic reviews (Online) · June 2013 DOI: 10.1002/14651858.CD009415.pub2 · Source: PubMed

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Zinc supplements for treating thalassaemia and sickle cell disease (Review) Swe KMM, Abas ABL, Bhardwaj A, Barua A, Nair NS

This is a reprint of a Cochrane review, prepared and maintained by The Cochrane Collaboration and published in The Cochrane Library 2013, Issue 6 http://www.thecochranelibrary.com

Zinc supplements for treating thalassaemia and sickle cell disease (Review) Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

TABLE OF CONTENTS HEADER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLAIN LANGUAGE SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . METHODS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Figure 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AUTHORS’ CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CHARACTERISTICS OF STUDIES . . . . . . . . . . . . . . . . . . . . . . . . . DATA AND ANALYSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analysis 1.1. Comparison 1 Zinc versus placebo (thalassaemia), Outcome 1 Serum zinc level. . . . . Analysis 1.2. Comparison 1 Zinc versus placebo (thalassaemia), Outcome 2 Body mass index. . . . . Analysis 1.3. Comparison 1 Zinc versus placebo (thalassaemia), Outcome 3 Height velocity. . . . . . Analysis 2.1. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 1 Haemoglobin. . . . . Analysis 2.2. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 2 Serum zinc level. . . . Analysis 2.3. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 3 Serum zinc level. . . . Analysis 2.4. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 4 Body mass index. . . . Analysis 2.5. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 5 Weight. . . . . . . Analysis 2.6. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 6 Sickle cell crisis. . . . Analysis 2.7. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 7 Total number of infection. Analysis 2.8. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 8 Total number of infection. Analysis 2.9. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 9 Improvement in leg ulcer. ADDITIONAL TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CONTRIBUTIONS OF AUTHORS . . . . . . . . . . . . . . . . . . . . . . . . . DECLARATIONS OF INTEREST . . . . . . . . . . . . . . . . . . . . . . . . . .


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[Intervention Review]

Zinc supplements for treating thalassaemia and sickle cell disease Kye Mon Min Swe1 , Adinegara BL Abas1 , Amit Bhardwaj2 , Ankur Barua3 , N S Nair4 1 Department of Community Medicine, Melaka-Manipal Medical College (MMMC), Melaka, Malaysia. 2 Department of Orthopaedics,

Melaka-Manipal Medical College (MMMC), Melaka, Malaysia. 3 Department of Community Medicine, International Medical University (IMU), Kuala Lumpur, Malaysia. 4 Department of Statistics, Manipal University, Manipal, India Contact address: Kye Mon Min Swe, Department of Community Medicine, Melaka-Manipal Medical College (MMMC), Jalan Batu Hampar, Bukit Baru, Melaka, 75150, Malaysia. [email protected]. Editorial group: Cochrane Cystic Fibrosis and Genetic Disorders Group. Publication status and date: New, published in Issue 6, 2013. Review content assessed as up-to-date: 20 June 2013. Citation: Swe KMM, Abas ABL, Bhardwaj A, Barua A, Nair NS. Zinc supplements for treating thalassaemia and sickle cell disease. Cochrane Database of Systematic Reviews 2013, Issue 6. Art. No.: CD009415. DOI: 10.1002/14651858.CD009415.pub2. Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

ABSTRACT Background Haemoglobinopathies, inherited disorders of haemoglobin synthesis (thalassaemia) or structure (sickle cell disease), are responsible for significant morbidity and mortality throughout the world. The WHO estimates that, globally, 5% of adults are carriers of a haemoglobin condition, 2.9% are carriers of thalassaemia and 2.3% are carriers of sickle cell disease. Carriers are found worldwide as a result of migration of various ethnic groups to different regions of the world. Zinc is an easily available supplement and intervention programs have been carried out to prevent deficiency in people with thalassaemia or sickle cell anaemia. It is important to evaluate the role of zinc supplementation in the treatment of thalassaemia and sickle cell anaemia to reduce deaths due to complications. Objectives To assess the effect of zinc supplementation in the treatment of thalassaemia and sickle cell disease. Search methods We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group’s Haemoglobinopathies Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Date of most recent search: 01 February 2013. Selection criteria Randomised, placebo-controlled trials of zinc supplements for treating thalassaemia or sickle cell disease administered at least once a week for at least a month. Data collection and analysis Two review authors assessed the eligibility and risk of bias of the included trials, extracted and analysed data and wrote the review. We summarised results using risk ratios or rate ratios for dichotomous data and mean differences for continuous data. We combined trial results where appropriate. Zinc supplements for treating thalassaemia and sickle cell disease (Review) Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

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Main results We identified nine trials for inclusion with all nine contributing outcome data. Two trials reported on people with thalassaemia (n = 152) and seven on sickle cell anaemia (n = 307). In people with thalassaemia, in one trial, the serum zinc level value showed no difference between the zinc supplemented group and the control group, mean difference 47.40 (95% confidence interval -12.95 to 107.99). Regarding anthropometry, in one trial, height velocity was significantly increased in patients who received zinc supplementation for one to seven years duration, mean difference 3.37 (95% confidence interval 2.36 to 4.38) (total number of participants = 26). In one trial, however, there was no difference in body mass index between treatment groups. Zinc acetate supplementation for three months (in one trial) and one year (in two trials) (total number of participants = 71) was noted to increase the serum zinc level significantly in patients with sickle cell anaemia, mean difference 14.90 (95% confidence interval 6.94 to 22.86) and 20.25 (95% confidence interval 11.73 to 28.77) respectively. There was no significant difference in haemoglobin level between intervention and control groups, at either three months (one trial) or one year (one trial), mean difference 0.06 (95% confidence interval -0.84 to 0.96) and mean difference -0.07 (95% confidence interval -1.40 to 1.26) respectively. Regarding anthropometry, one trial showed no significant changes in body mass index or weight after one year of zinc acetate supplementation. In patients with sickle cell disease, the total number of sickle cell crises at one year were significantly decreased in the zinc sulphate supplemented group as compared to controls, mean difference -2.83 (95% confidence interval -3.51 to -2.15) (total participants 130), but not in zinc acetate group, mean difference 1.54 (95% confidence interval -2.01 to 5.09) (total participants 22). In one trial at three months and another at one year, the total number of clinical infections were significantly decreased in the zinc supplemented group as compared to controls, mean difference 0.05 (95% confidence interval 0.01 - 0.43) (total number of participants = 36), and mean difference -7.64 (95% confidence interval -10.89 to -4.39) (total number of participants = 21) respectively. Authors’ conclusions According to the results, there is no evidence from randomised controlled trials to indicate any benefit of zinc supplementation with regards to serum zinc level in patients with thalassaemia. However, height velocity was noted to increase among those who received this intervention. There is mixed evidence on the benefit of using zinc supplementation in people with sickle cell disease. For instance, there is evidence that zinc supplementation for one year increased the serum zinc levels in patients with sickle cell disease. However, though serum zinc level was raised in patients receiving zinc supplementation, haemoglobin level and anthropometry measurements were not significantly different between groups. Evidence of benefit is seen with the reduction in the number of sickle cell crises among sickle cell patients who received one year of zinc sulphate supplementation and with the reduction in the total number of clinical infections among sickle cell patients who received zinc supplementation for both three months and for one year. The conclusion is based on the data from a small group of trials,which were generally of good quality, with a low risk of bias. The authors recommend that more trials on zinc supplementation in thalassaemia and sickle cell disease be conducted given that the literature has shown the benefits of zinc in these types of diseases.

PLAIN LANGUAGE SUMMARY Zinc supplements for thalassaemia and sickle cell disease Zinc is an essential micronutrient, which is needed so that the immune system works at its best and helps the body fight off infection. People may not get enough zinc from food alone. Researchers have therefore looked at zinc supplements as a way of reducing anaemia and preventing infections and complications. The review authors searched the medical literature for randomised controlled studies in which people with sickle cell disease or thalassaemia received either zinc supplements or no supplements. We included nine trials in the review (459 participants). In people with thalassaemia, there is no evidence to indicate any benefit of zinc supplements on serum zinc level. However, there was an improvement in height in those who received the supplements. There is mixed evidence on the benefit of using zinc supplements in people with sickle cell disease. For instance, there is evidence that when supplements are given for one year the serum zinc levels increased; however, haemoglobin levels and body mass index did not differ significantly between groups. We also found that people with sickle cell disease who received zinc supplements (at both three months and at one year) had fewer sickle cell crises and infections. However, given that the total number of trials is small, these results should be treated with caution. Zinc supplements for treating thalassaemia and sickle cell disease (Review) Copyright © 2013 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

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BACKGROUND

expected low serum zinc level is due to haemolysis, loss in urine and inadequate dietary intake (Prasad 1965).

Description of the condition Haemoglobinopathies, inherited disorders of haemoglobin synthesis (thalassaemia) or structure (sickle cell disorders), are responsible for significant morbidity and mortality all over the world (Tracey 2005). The WHO estimates that globally 5% of adults are carriers of a haemoglobin condition, 2.9% of thalassaemia and 2.3% of sickle cell disease (WHO 2006). Carriers are found worldwide as a result of migration of various ethnic groups to different regions of the world (Stewart 2007). Sickle cell haemoglobinopathies are heredity disorders in which red cells contain haemoglobin S, due to a mutation in the betaglobin gene. There are different types of sickle cell disease (SCD) (e.g. sickle cell anaemia (SS), sickle cell haemoglobin C (SC), sickle cell beta thalassaemia (SBThal), etc) and these can be diagnosed with blood tests or genetic testing. In SCD, the red blood cells become rigid and distorted assuming a sickle shape. This leads to a reduction in oxygen-carrying capacity and these abnormal cells block the blood vessels resulting in tissue hypoxia and consequent pain. Symptoms such as severe anaemia, susceptibility to infections and damage to major organs are also seen. Treatment involves managing the anaemia, chronic pain, and organ damage caused by SCD. Thalassaemia is a heterogeneous group of disorders with a genetically determined reduction in one or more types of haemoglobin polypeptide chain, resulting in a decrease in the amount of haemoglobin involving the affected chain. The most common types are alpha and beta thalassaemia. Children affected with thalassaemia show no symptoms at birth, but anaemia emerges in the first few months of life, becoming progressively severe and leading to pallor, easy fatigability, failure to thrive, a delay in maturity and fever. Treatment based on blood transfusions is helpful but not curative. Early treatment of thalassaemia has proved to be very effective in improving the quality of life of patients (Firkin 1989). The low haemoglobin in SCD and thalassaemia patients is obviously due to haemolysis caused by the genetic mutation of haemoglobin, and hence one should not expect haemoglobin levels to increase following zinc supplementation. Zinc is primarily an intracellular component and hence decreased plasma levels of zinc are not necessarily markers of zinc deficiency. Red blood cells, neutrophils and platelets are very rich in zinc. Plasma zinc assays are unreliable unless the blood is processed within two hours after collection.In vitro haemolysis of blood samples from patients with SCD after two hours of collection raises the plasma zinc level thus obscuring the distinction between people who are zinc-sufficient and those who are zinc-deficient. Zinc deficiency is best diagnosed by the decreased content of intracellular zinc in red blood cells, neutrophils and platelets. Moreover, patients with SCD also have hyperzincuria which contributes to zinc deficiency (Prasad 1966; Prasad 1975). In thalassaemia, the

Description of the intervention Zinc is one of the essential micronutrients in humans and acts as a co-factor for more than 300 enzymes. It plays a particular role in human growth and development. Zinc is present in all tissues, fluids, and secretions in the body and is critical to cellular metabolism, physical growth, immune-competence, reproductive functions, integrity of intestinal mucosa and neuro-behavioural development (Mahyar 2010). Zinc has several roles in biochemical and hormonal functions of various endocrine organs (Prasad 1985). Zinc deficiency is observed in pathological conditions including haemoglobinopathies. Many studies have shown that zinc deficiency is fairly common in patients with SCD (Daeschner 1981; Phebus 1988). Patients with beta thalassaemia major suffer from zinc deficiency which could be seen as one of the causes of delayed maturity. Zinc deficiency is also found in patients with SCD and several clinical manifestations of this disorder have been subsequently related to it. The daily requirement of zinc varies with age. For adults, the recommended dietary allowance (RDA) of 15 mg daily is regarded as adequate to prevent deficiencies. For infants and children aged seven to 10 years, the RDA is 7 mg and 10 mg per day respectively (RDA 1989). A number of zinc supplements are available, with zinc sulphate being the most frequently used (Aggett 1995; Bhatangar 2004). The recommended dose of zinc supplementation for optimal effects on incidences of infection and pain crises is usually 50 mg to 75 mg elemental zinc daily. This dose of zinc could be associated with copper deficiency. If the dose of elemental zinc is greater than 50 mg/d, 1 mg of elemental copper as sulfate should be added to the regimen to prevent copper deficiency.

How the intervention might work In cases of thalassaemia, zinc supplementation corrects the risk of zinc deficiency from various causes including desferrioxamine injections. Studies have shown that zinc supplementation in patients with thalassaemia increases bone mass, improves linear growth and corrects immunodeficiency and growth delay. For SCD, studies have shown that zinc can improve the sickle cell membrane status, antagonise intracellular calcium, and affect red cell dehydration (Bennekou 2001). Studies have demonstrated a significant reduction in the number of sickle-related events in people treated with zinc sulphate and also suggested a benefit for other problems in SCD, including leg ulcers, growth, infection and androgen deficiency in male participants (Nagalla 2010). Zinc supplementation has also been found to decrease the incidence of infection and pain crises by correcting T helper 1 functions and


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cell-mediated immunity (Prasad 1999). In addition, improvement in the rate of linear growth has been demonstrated after zinc supplementation in pre-pubertal children with SCD (Zemel 2002). Zinc also facilitates red cell deformability, so that in the case of haemoglobinopathies, there is a reduction in the amount of red cells destroyed by the spleen. For haemoglobinopathies, some evidence suggests that preventive zinc supplementation may reduce mortality and morbidity, particularly in sickle cell anaemia and thalassaemia (Arcasoy 1987).

Types of interventions Oral zinc supplements regardless of dosage and type versus oral supplements without zinc (placebo). Types of outcome measures

Primary outcomes

Thalassaemia

Why it is important to do this review It has been estimated that approximately 5% of the world’s population are carriers of haemoglobinopathies (WHO 2006) and that 300,000 to 400,000 babies with severe forms of these diseases are born each year. If left untreated these result in death in the first few years of life (WHO 1989). Various studies have found beneficial effects of zinc supplementation to zinc-deficient SCD and thalassaemia patients (Arcasoy 1987; Prasad 2007; Zemel 2002). Zinc is an easily available supplement; and intervention programs have been carried out to prevent deficiency in people with thalassaemia or sickle cell anaemia. It is important to evaluate the role of zinc supplementation in the treatment of thalassaemia and SCD to reduce deaths due to complications.

OBJECTIVES To assess the effect of zinc supplementation in the treatment of thalassaemia and SCD.

METHODS

Criteria for considering studies for this review Types of studies Randomised control trials (RCTs) and controlled clinical trials. Types of participants People of all ages who have been diagnosed with thalassaemia or SCD. Diagnosis of SCD, sickle cell trait and thalassaemia can be done through blood testing, using a technique called haemoglobin electrophoresis; Hb-S may be demonstrated on cellulose acetate at PH 8.6 between Hb A and Hb A2 in SCD and the amount of Hb A2 level and Hb F will increase in different types of thalassaemia (Firkin 1989).

1. Haemoglobin level 2. Serum zinc level 3. Anthropometry measurements Sickle cell disease 1. Haemoglobin level 2. Serum zinc level 3. Anthropometry measurements Secondary outcomes

Thalassaemia 1. Bone mineral index 2. Frequency of blood transfusion 3. Duration of blood transfusion Sickle cell disease 1. Number of sickle cell crises 2. Complications due to underlying disease (e.g. infection, renal effects, red blood cell dehydration, leg ulcers) 3. Quality of life

Search methods for identification of studies Electronic searches Relevant studies were identified from the Cystic Fibrosis & Genetic Disorders Review Group’s Haemoglobinopathies Trials Register using the term: zinc. The Haemoglobinopathies Trials Register is compiled from electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (updated each new issue of The Cochrane Library) and quarterly searches of MEDLINE. Unpublished work is identified by searching the abstract books of five major conferences: the European Haematology Association conference; the American Society of Hematology conference; the British Society for Haematology Annual Scientific Meeting; the Caribbean Health Research


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Council Meetings; and the National Sickle Cell Disease Program Annual Meeting. For full details of all searching activities for the register, please see the relevant section of the Cystic Fibrosis and Genetic Disorders Group Module. Date of the last search: 01 February 2013. Searching other resources References of the identified relevant trials were scrutinized for additional citations. We contacted organisations and researchers working in this field as well as manufacturers of zinc supplements to identify additional trials (including unpublished and ongoing trials).

Data collection and analysis

Selection of studies The review authors (KM and ALA) independently assessed trial eligibility and screened all available titles and abstracts for inclusion using an eligibility form designed in accordance with the specified inclusion criteria. For those trials we were unable to ascertain the relevance of by simply screening the title and abstract, we retrieved and reviewed the full text of the articles. We resolved disagreements by discussion and by consultation with a third review author. We also displayed trials excluded from the review in the form of a table along with the reason for exclusion.

Measures of treatment effect For dichotomous data, we presented results as odds ratios (OR) with 95% confidence intervals (CIs). For continuous data, where outcomes were measured in the same way between trials, we used the mean difference (MD) with 95% CIs. Where publications presented the MD and standard error (SE), we calculated the standard deviation (SD). One cross-over trial was included in the review and reported data for one of the review’s primary outcomes (serum zinc level). These data were presented for each individual and we calculated the MD and the SE for each treatment arm and entered these data into the meta-analysis using the generic inverse variance method. For future updates, when appropriate, we plan to use the standardized mean difference (SMD) to combine trials that measured the same outcome, but used different methods (Higgins 2011). For count data we calculated the MD. Unit of analysis issues In this review we have treated the participant as the unit of analysis. This is important as the meta-analytic techniques used assume independence between measurements, and more than one treated event (e.g. ’crisis’) per participant would not be statistically independent. A result of ignoring this unit of analysis issue could be overly optimistic CIs. Where the data are reported as events, rather than as participants, we have reported these data within an additional table. Dealing with missing data

Data extraction and management Two review authors (KM and AB) independently collected the data (trial characteristics and results), for thalassaemia and SCD separately, compared the results and corrected errors. We resolved disagreements through discussion, and by consultation with the third review author. We planned to report outcomes at up to one month, over one month to three months, over three months to six months and over six months to one year and more than one year. They were to also consider additional follow-up data recorded at other time periods. However, in the current version of the review we were only able to include three-month, six-month and oneyear data as provided in the included trials. Assessment of risk of bias in included studies Two authors (KM, ALA) independently assessed the risk of bias of the included trials by using the criteria outlined in the Cochrane Handbook of Systematic Reviews of Interventions (Higgins 2011). We assessed sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reporting and other potential sources of bias. We also judged each domain as having either a ‘low risk’, ‘high risk, or ‘unclear risk’ of bias.

In order to allow an intention-to-treat analysis, we searched for full reports from the investigators where trials have been published in abstract form only, presented at meetings or reported to the coauthors. Where information was missing or unclear, we contacted the investigators for further details. Assessment of heterogeneity We used the Chi2 test for heterogeneity (significance level P < 0.1) and quantify the degree of heterogeneity by means of the I2 statistic. We used the following guidelines for the interpretation of the I2 values (Higgins 2011): 0% to 40%: might not be important; 30% to 60%: may represent moderate heterogeneity; 50% to 90%: may represent substantial heterogeneity; 75% to 100%: considerable heterogeneity. Where the I2 value was at 50% or more, we regarded as significant heterogeneity. Assessment of reporting biases We did comprehensive searches in an attempt to minimise publication and reporting biases and the likelihood of these biases


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will be considered. Within studies, selective outcome reporting was considered as part of risk of bias assessment. We compared the ’Methods’ section of the full published paper to the ’Results’ section to ensure that all outcomes which were measured, were reported. We planned to assess publication bias by using a funnel plot. However, there were insufficient trials with similar outcome measures to undertake these analyses.

Data synthesis Where trials were clinically and methodologically comparable, we carried out meta-analysis using the Review Manager software ( RevMan 2011). Given there was no significant heterogeneity and trials were sufficiently similar, the authors used a fixed-effect metaanalysis model for combining data. For future updates, if we find significant heterogeneity, we plan to use a random-effects model.

4. Different types of complication (infection, sickle cell crisis, leg ulcers, linear growth) Sensitivity analysis We planned to carry out a sensitivity analysis to explore the effect of the risk of bias of the trials (assessed by concealment of allocation), by excluding trials with a high risk of bias for this domain. However, there were insufficient trials with similar outcome measures to do this analysis in this version of the review.

RESULTS

Description of studies Subgroup analysis and investigation of heterogeneity Providing there were sufficient trials, and if we found significant heterogeneity, we planned to carry out the subgroup analyses listed below, however, there were insufficient trials with similar outcome measures to undertake these analyses. We plan to undertake these subgroup analyses in future versions of the review if there are a sufficient number of trials included for either disease (10 or more). 1. Different durations of zinc supplementation (less than three months, three months to one year, one year to five years) 2. Different doses of zinc used (low dose versus high dose) 3. Haemoglobin level of participants (baseline haemoglobin level less than 10 mg/dl and more than 10 mg/dl)

Results of the search We identified 17 records of which 11 records were identified through database searching and another six were identified through other sources such as MEDLINE and PubMed. From this list, we removed three records that were considered as duplicates, leaving us a total of 14 trials. We proceeded to obtain the full text of all 14 trials. Following the assessment of these full text articles, we considered nine trials (published in eight papers) for inclusion in this review and excluded six trials. We listed one trial (zinc and bone health in thalassaemia by the Children’s Hospital and Research Centre Oakland (NCT00459732)) as ongoing (Figure 1).


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Figure 1. Study flow diagram


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Included studies We identified nine trials that met our inclusion criteria. Two of these trials were in patients with thalassaemia (Acrasoy 1987; Rashidi 2011) (n = 152) and the remaining seven trials were in patients with sickle cell anaemia (n = 307) (Bao 2008; Gupta 1995; Prasad 1981 (1); Prasad 1981 (2); Prasad 1999; Serjeant 1970; Zemel 2002). The 1981 Prasad paper reported on two separate trials (Prasad 1981 (1); Prasad 1981 (2)).

Thalassaemia

Two trials were on individuals with thalassaemia (Acrasoy 1987; Rashidi 2011). One trial was a RCT conducted at a Turkish hospital (Acrasoy 1987), while another was double-blind RCT conducted in the Golestan province in northern Iran (Rashidi 2011). In the Acrasoy study, zinc acetate in the form of 22.5 mg elemental zinc in gelatin capsules was used, while in the Rashidi trial, 220 mg zinc sulphate containing 50 mg zinc daily for three months was used (Acrasoy 1987; Rashidi 2011). In the Acrasoy trial the duration of zinc therapy ranged from one to seven years in both groups and linear growth of all patients was assessed in to comparison with the growth curves of Turkish children (Acrasoy 1987). In the Rashidi trial, zinc supplementation was given over a threemonth period (Rashidi 2011). Regarding age, in Acrasoy trial, the age range was from 1 to 18 years (Acrasoy 1987) and in Rashidi trial, the participants were over 18 years of age (Rashidi 2011).The outcomes in the Acrasoy trial centred mainly on growth (height velocity) (Acrasoy 1987), while the outcomes for the Rashidi trial were serum zinc levels, serum vitamin E levels and enzymes, such as super oxide dismutase activity and total antioxidant capacity activity (Rashidi 2011).

Sickle cell disease

Seven trials were on individuals with sickle cell anaemia (Bao 2008; Gupta 1995; Prasad 1981 (1); Prasad 1981 (2); Prasad 1999; Serjeant 1970; Zemel 2002). One trial was conducted in India (Gupta 1995), one in Jamaica (Serjeant 1970) and the remaining five in the USA (in regions of Detroit and Philadelphia). There were six parallel trials and one cross-over trial (Prasad 1981 (1)). Regarding the type of zinc used, in five trials the intervention groups received zinc acetate (Bao 2008; Prasad 1981 (1); Prasad

1981 (2); Prasad 1999; Zemel 2002) and in remaining two trials zinc sulphate was used (Gupta 1995; Serjeant 1970). The duration of zinc supplementation varied (as well as the evaluation periods), the interval being three months for one trial (Bao 2008), six months for another (Serjeant 1970) and one year for the remaining four trials (Prasad 1981 (1); Prasad 1981 (2); Prasad 1999; Zemel 2002). The age range also varied across different trials; four of these recruited only adults: Bao 2008 (18 to 47 years); Prasad 1981 (1) and Prasad 1981 (2) (16 to 28 years); and Prasad 1999 (19 to 49 years). For a further trial the participants were over five years of age (Gupta 1995) and in the Zemel trial participants were aged 4 to 11 years (Zemel 2002). Serjeant did not report an age range (Serjeant 1970). Regarding the outcomes across trials, three trials had similar outcomes (Bao 2008; Gupta 1995; Prasad 1999). Gupta measured sickle cell crises as the primary outcome (Gupta 1995), Prasad measured the total number of sickle cell crises and the total number of infections (Prasad 1999) and Bao hypothesized that zinc supplementation would promote the immune system and measured the number of sickle cell crises and the number of infections (Bao 2008). Two trials by Prasad assessed the effect of serum testosterone level in zinc supplementation and measured serum zinc level in SCD patients as one of the outcomes (Prasad 1981 (1); Prasad 1981 (2)). The major outcome of the trial was the improvement of leg ulcers in patients with SCD (Serjeant 1970); and Zemel measured for growth and body composition, especially height, in prepubertal children after supplementation with zinc (Zemel 2002).

Excluded studies There were a total of four trials excluded (Mehdizadeh 2008; Prasad 1975; Prasad 1983a; Tschumi 1981). Three trials were not RCTs (Mehdizadeh 2008; Prasad 1975; Prasad 1983a) and the fourth trial did not include individuals with SCD or thalassaemia (Tschumi 1981).

Risk of bias in included studies Please refer to the figures for an overall assessment of the risk of bias (Figure 2; Figure 3).


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Figure 2. Risk of bias graph: review authors’ judgements about each risk of bias item presented as percentages across all included studies.


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Figure 3. Risk of bias summary: review authors’ judgements about each risk of bias item for each included study.


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Allocation All of the trials reported the use of randomisation techniques, however, only two provided further details of these and we therefore assessed these as having a low risk of bias in this domain (Gupta 1995; Rashidi 2011). We have assessed the remaining four trials as having an unclear risk of bias for this domain (Acrasoy 1987; Bao 2008; Prasad 1999; Zemel 2002). None of the included trials described the method of allocation concealment and we have therefore assessed all as having an unclear risk of bias.

Blinding Six of the nine trials included in the analysis reported the use of a double-blinding procedure during the trial (blinding of some or all relevant individuals involved in the trial) (Bao 2008; Gupta 1995; Prasad 1981 (1); Prasad 1981 (2); Serjeant 1970; Rashidi 2011) (we have classified five trials as having a low risk of bias for the blinding of participants, personnel and outcome assessors, and one trial as having a low risk of bias for participants and personnel and an unclear risk for outcome assessors). The remaining three trials did not provide details of the blinding procedure and were therefore categorised as having an unclear risk of bias (Acrasoy 1987; Prasad 1999; Zemel 2002).

Incomplete outcome data Six of nine trials included in the analysis had complete outcome data (Acrasoy 1987; Bao 2008; Prasad 1981 (1); Prasad 1981 (2); Prasad 1999; Rashidi 2011). The remaining three trials presented incomplete outcome data (Gupta 1995; Serjeant 1970; Zemel 2002). We regarded two of these trials as adequately accounting for the incomplete data (Serjeant 1970; Zemel 2002) but the third trial did not account for the 10% of recruited participants who were lost to follow up. (Gupta 1995). Therefore, we classified five trials as having a low risk of bias for this domain (Acrasoy 1987; Bao 2008; Prasad 1981 (1); Prasad 1981 (2); Prasad 1999; Rashidi 2011; Serjeant 1970; Zemel 2002) and one as having an unclear risk of bias (Gupta 1995).

Other potential sources of bias None of the included trials reported any other potential sources of bias. There was no clear evidence of any other bias in any of the trials included in the analysis.

Effects of interventions

Thalassaemia We identified two trials (n = 152) for inclusion (Acrasoy 1987; Rashidi 2011). Zinc acetate was supplemented in the first trial (n = 32) (Acrasoy 1987) and zinc sulphate in the second (n = 120) (Rashidi 2011).

Primary outcomes

1. Haemoglobin level This outcome was not assessed in either of the included trials (Acrasoy 1987; Rashidi 2011).

2. Serum zinc level One trial reported on this outcome (Rashidi 2011). There was no significant difference noted in serum zinc level between the group receiving zinc sulphate supplementation and control group, MD 47.70 (95% CI -12.59 to 107.99) (Rashidi 2011) (Analysis 1.1).

3. Anthropometry measurement One trial reported on body mass index (Rashidi 2011). In the analysis of body mass index there was no significant difference observed between the group receiving zinc sulphate supplementation and the control group, MD 0.70 (95% CI -0.55 to 1.95) (60 participants included) (Rashidi 2011) (Analysis 1.2). Regarding height velocity, Acrasoy reported that this was significantly increased in patients who acquired zinc acetate supplementation for one year duration, MD 3.37 (95% CI 2.36 to 4.38) (Acrasoy 1987) (Analysis 1.3).

Secondary outcomes

Selective reporting None of the trials included in the analysis showed any evidence of selective reporting, although this was difficult to assess because the outcomes of interest in this review were not the primary outcomes of any of the trials.

1. Bone mineral index This outcome was not assessed in either of the included trials (Acrasoy 1987; Rashidi 2011).


11

2. Frequency of blood transfusion This outcome was not assessed in either of the included trials (Acrasoy 1987; Rashidi 2011).

value with no SD was reported. There was also not enough data to consider imputation of the SD.

3. Anthropometry measurement 3. Duration of blood transfusion This outcome was not assessed in either of the included trials (Acrasoy 1987; Rashidi 2011).

Sickle cell disease We identified seven trials (n = 307) for inclusion (Bao 2008; Gupta 1995; Prasad 1981 (1), Prasad 1981 (2) Prasad 1999; Serjeant 1970; Zemel 2002). Zinc acetate was supplemented in five trials (n = 128) (Bao 2008; Prasad 1981 (1); Prasad 1981 (2); Prasad 1999; Zemel 2002) and zinc sulphate in two trials (n = 179) (Gupta 1995; Serjeant 1970).

One trial reported on this outcome (Zemel 2002). There was no significant difference observed with regards to body mass index between the group receiving zinc acetate supplementation and control group, MD 0.00 (95% CI -1.13 to 1.13) (Zemel 2002) (Analysis 2.4). As for weight, there was no significant difference observed between zinc acetate supplementation and control group, MD -1.50 (95% CI -5.07 to 2.07) (Zemel 2002) (Analysis 2.5).

Secondary outcomes

1. Number of sickle cells crises Primary outcomes

1. Haemoglobin level Two trials included analysis of haemoglobin level (Bao 2008; Prasad 1999). In one trial, the duration of zinc acetate supplementation was three months and there was no significant difference noted between the group receiving zinc acetate supplementation and control group in haemoglobin level, MD 0.06 (95% CI -0.84 to 0.96) (Bao 2008) (Analysis 2.1). In the Prasad trial there was no significant difference noted between the group receiving zinc acetate supplementation and control group in haemoglobin level, MD - 0.07 (95% CI -1.40 to 1.26) (Prasad 1999) (Analysis 2.1). The Gupta trial (zinc sulphate) reported haemoglobin concentration as a percentage; however, only the mean value was reported, there was no report of the SD (Gupta 1995). There was also not enough data to consider imputation of the SD.

Two trials reported on number of sickle cell crises (Gupta 1995; Prasad 1999). The Gupta trial on zinc sulphate supplementation reported a reduction in the number of crises at three months, for those receiving zinc sulphate supplementation (n = 65) as compared to the control group (n = 65) (Gupta 1995). Given the ’crisis’ was the unit of analysis for this outcome we are not able to enter these data into RevMan and they are instead are provided in an additional table (Table 1). Only two trials reported on the mean number of sickle cell crises at one year, the group receiving zinc supplementation was noted to have significantly fewer crises as compared to control group, MD -2.83 (95% CI -3.51 to -2.15) (n = 130) (P < 0.00001) for zinc sulphate, but no significant difference was noted in zinc acetate group, MD 1.54 (95% CI -2.01 to 5.09) (n = 22) (Gupta 1995; Prasad 1999) (Analysis 2.6).

2. Complications due to underlying disease (e.g. infection, renal effects, red blood cell dehydration, leg ulcers) 2. Serum zinc level Four trials reported analysis of serum zinc level (Bao 2008; Prasad 1981 (1); Prasad 1981 (2); Prasad 1999). In one trial with a threemonth intervention (zinc acetate), there were significant increases in serum zinc level, MD 14.90 (95% CI 6.94 to 22.86) (Bao 2008); and in two further trials the group receiving zinc acetate supplementation for one year had significantly higher serum zinc levels as compared to the control group, MD 20.25 (95% CI 11.73 to 28.77) (Prasad 1981 (2); Prasad 1999 ) (Analysis 2.2). In the remaining trial (a cross-over trial) the results show a significant difference in favour of zinc acetate supplementation, MD -35.00 (95%CI -53.95 to -16.05) (Prasad 1981 (1)) (Analysis 2.3). The Gupta trial (zinc sulphate) did actually report serum zinc level in microgram per decilitre (Gupta 1995). However, only the mean

Infection Three trials reported on this outcome (Bao 2008; Prasad 1999; Serjeant 1970). For the number of clinical infections at three months, the group receiving zinc acetate supplementation was found to have fewer infections as compared to the control group, OR 0.05 (95% CI 0.01 to 0.43) (Bao 2008) (Analysis 2.7). Similarly, at one year, with regards to the number of clinical infections, the group receiving zinc acetate supplementation was found to have fewer infections as compared to the control group, MD 7.64 (95% CI -10.89 to -4.39) (Prasad 1999) (Analysis 2.8).


12

One trial reported on the improvement of leg ulcers (Serjeant 1970). The group receiving zinc sulphate supplementation was found to have more healing leg ulcers as compared to the control group, OR 4.06 (95% CI 0.63 to 26.13) (Analysis 2.9).

Currently, there are limited treatment options for patients with SCD to prevent both infection and painful crises, the two most difficult complications of this disease; zinc seems to be the only therapeutic option available at present.

3. Quality of life

Quality of the evidence

This outcome was not assessed in any of the included trials.

DISCUSSION

Summary of main results We identified nine trials for inclusion and all nine contributed some outcome data. Four out of seven trials, on sickle cell anaemia, showed an increase in the level of zinc amongst the intervention group as compared to the control group (Bao 2008; Prasad 1981 (1); Prasad 1981 (2); Prasad 1999). However, caution is required when interpreting this finding as the raised plasma zinc level may be associated with intravascular haemolysis in blood samples of patients that were not processed immediately (Prasad 1983b). Regarding anthropometry, there was no significant change in either body mass index or weight after one year of zinc supplementation. However, height velocity was noted to be significantly increased in patients who received zinc supplementation for one year duration. The mean number of sickle cell crises were significantly decreased in the zinc sulphate (but not the zinc acetate) supplementation group in comparison with the control group in SCD patients after one year of zinc supplementation. The total number of clinical infections were significantly decreased in the zinc supplementation group in comparison with the control group in SCD patients after three months and one year of zinc supplementation. A significant improvement in the healing of ulcers was found by Serjeant in the zinc supplementation group in comparison with the control group in people with SCD (Serjeant 1970). Two trials assessed patients with thalassaemia. In one trial, neither the serum zinc level value nor body mass index showed a difference between zinc supplemented group and control group. However, in the second trial, height velocity was significantly increased in patients who received zinc supplements for between one and seven years.

Overall completeness and applicability of evidence Although the total number of trials is small, the overall conclusion is that zinc supplementation gave mixed evidence on beneficial effects in both sickle cell anaemia and beta thalassaemia patients.

The trial evidence included is generally of good quality, with a low risk of bias. Four of the eight trials reported detailed explanations on blinding procedures. Three of the eight included trials were found to have some degree of loss to follow up (Gupta 1995; Serjeant 1970; Zemel 2002). However, given we regarded an overall attrition rate of greater than 20% to indicate a high risk of bias (Thomas 2006), on this basis these three trials (for this domain) were considered to be of low risk of bias. The majority of the trials were carefully conducted hospital-based trials, with active mechanisms in place to promote adherence to the intervention, and active-case finding. However, although all of the trials reported the use of randomised methods, the majority did not elaborate on the method used nor on the allocation concealment methods employed.

Potential biases in the review process Although zinc supplementation in SCD patients was observed to improve serum zinc level and reduce complications such as number of sickle cell crises and clinical infections, there were some limitations noted in the trials. For instance, there were variations with regards to the the duration of zinc supplementations received. To reduce bias, we used the results of zinc supplementation at three months, six months and one year. The age of the participants was also not homogenous, but due to the limited number of included trials our planned subgroup analysis was not possible. In addition, there were two types of zinc used as supplements (zinc sulphate and zinc acetate), which were not combined; furthermore, these were of different doses. Another limitation of the trials was the lack of reported data, which highlights the need for better reporting of trials.

Agreements and disagreements with other studies or reviews We are unaware of similar reviews covering this topic.

AUTHORS’ CONCLUSIONS Implications for practice There is evidence that, in SCD, zinc sulphate is associated with an increased serum zinc level after supplementation of zinc for one


13

year and also with a reduction in pain crises and other complications such as infections. This was despite the treatment not being associated with an improvement in any of the haematological outcomes. Zinc is the only possible therapeutic modality available at present, the use of which is supported by this review. In thalassaemia, there has been no evidence to indicate that zinc supplementation will lead to an increased serum zinc level, but there has been an improvement in some anthropometry measurements.

Implications for research Initial results do seem to favour zinc supplementation in patients with SCD; however further trials need to be conducted to improve the validity of the review. For instance, multicentre RCTs of zinc

supplementation should be conducted in both patients with SCD and thalassaemia. To investigate whether the findings previously reported were consistent and sustained, these future trials should involve more participants and should have a longer duration of zinc supplementation than those reported in this review.

ACKNOWLEDGEMENTS We would like to thank Professor Datuk Dr. Abdul Razzak, the Chief Executive of Melaka-Manipal Medical College and Professor Dr. Jaspal Singh Sahota, Dean of Melaka-Manipal Medical College (MMMC) Malaysia for providing administrative support and helping us with their constant encouragement, meticulous supervision and constructive comments on this protocol.

REFERENCES

References to studies included in this review Acrasoy 1987 {published data only} Arcasoy A, Cavdar A, Cin S, Erten J, Babacan E, Gözdasoglu S, et al. Effect of zinc supplementation on linear growth in beta thalassaemia. American Journal of Hematology 1987;24(2):127–36. Bao 2008 {published data only} Bao B, Prasad A, Beck FWJ, Swerdlow PTI. Beneficial effect of zinc supplementation on oxidative stress, cytokines and NF-KB DNA binding in sickle cell disease patients [abstract]. Blood 2006;108(11):Abstract number: 1203. Gupta 1995 {published data only} Gupta VL, Chaubey BS. Efficacy of zinc therapy in prevention of crisis in sickle cell anemia: a double blind, randomized controlled clinical trial. Journal of the Association of Physicians of India 1995;43(7):467–9. Prasad 1981 (1) {published data only} Prasad AS, Abbasi AA, Rabbani P, Dumouchelle E. Effect of zinc supplementation on serum testosterone level in adult male sickle cell anemia subjects. American Journal of Hematology 1981;10(2):119–27. Prasad 1981 (2) {published data only} Prasad AS, Abbasi AA, Rabbani P, Dumouchelle E. Effect of zinc supplementation on serum testosterone level in adult male sickle cell anemia subjects. American Journal of Hematology 1981; Vol. 10, issue 2:119–27. [MEDLINE: 81204397] Prasad 1999 {published data only} Prasad AS, Beck FW, Kaplan J, Chandrasekar PH, Ortega J, Fitzgerald JT, et al.Effect of zinc supplementation on incidence of infections and hospital admissions in sickle cell disease (SCD). American Journal of Hematology 1999;61(3): 194–202.

Rashidi 2011 {published data only} Rashidi M, Aboomardani M, Rafraf M, Arefhosseini SR, Keshtkar A, Joshaghani H. Effects of vitamin E and zinc supplementation on antioxidants in beta thalassemia major patients. Iranian Journal of Pediatrics 2011;21(1):8–14. Serjeant 1970 {published data only} Serjeant GR, GRE, GMC. Oral zinc sulphate in sicklecell ulcers. Lancet 1970; Vol. 2, issue 7679:891–2. [MEDLINE: 71010522] Zemel 2002 {published data only} Fung E, Kawchak D, Zemel B, Ohene-Frempong K, Stallings V. Plasma zinc is not a sensitive indicator of zinc status in children with sickle cell disease [abstract]. Proceedings of the National Sickle Cell Disease Program Annual Meeting; 2001 April 2001:Abstract no: 82. ∗ Zemel BS, Kawchak DA, Fung EB, Ohene-Frempong K, Stallings VA. Effect of zinc supplementation on growth and body composition in children with sickle cell disease. American Journal of Clinical Nutrition 2002;75(2):300–7.

References to studies excluded from this review Mehdizadeh 2008 {published data only} Mehdizadeh M, Zamani G, Tabatabaee S. Zinc status in patients with major beta-thalassemia. Paediatria Haematology and Oncology 2008;25(1):49–54. Prasad 1975 {published data only} Prasad AS, Schoomaker EB, Ortega J, Brewer GJ, Oberleas D, Oelshlegel FJ. Zinc deficiency in sickle cell disease. Clinical Chemistry 1975;21(4):582–7. Prasad 1983a {published data only} Prasad AS, Cossack ZT. Zinc in sickle cell disease. Transactions of the Association of Americal Physicians 1983; 96:246–51.


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Tschumi 1981 {published data only} Tschumi P, Floersheim GL. Tolerance of large doses of oral zinc sulfate [Zur Vertraglichkeit von hochdosiertem peroralem Zinksulfat.]. Schweizerische Medizinische Wochenschrift 1981; Vol. 111, issue 42:1573–7. [MEDLINE: 82084437]

References to ongoing studies NCT00459732 {published data only} Fung EB. Zinc & Bone Health in Thalassemia: The Think Zinc Study (ThinkZn). clinicaltrials.gov (accessed 20 June 2013).

Additional references Aggett 1995 Aggett PJ, Comerford JG. Zinc and Human Health. Nutrition Reviews 1995;53(9 Pt 2):S16–S22. Arcasoy 1987 Arcasoy A, Cavdar A, Cin S, Erten J, Babacan E, Gözdasoglu S, et al.Effect of zinc supplementation on linear growth of beta thalassaemia. American Journal of Haematology 1987; 24(2):127–36. Bennekou 2001 Bennekou P, de Franceschi L, Pedersen O, Lian L, Asakura T, Evans G, et al.Treatment with NS3623, a novel Clconductance blocker,ameliorates erythrocyte dehydration in transgenic SAD mice: a possible new therapeutic approach for sickle cell disease. Blood 2001;97(5):1451–7. Bhatangar 2004 Bhatangar S, Natchu UC. Zinc in child health and disease. Indian Journal of Paediatrics 2004;71(11):991–5. Daeschner 1981 Daeschner CW 3rd, Matustik MC, Carpentieri U, Haggard ME. Zinc and growth in patients with sickle cell disease. Journal of Pediatrics 1981;98(5):778–80. Firkin 1989 Firkin F, Chesterman C, Peninton D, Rush B. de Gruchy’s Clinical Haematology in Medical Practice. 5th Edition. Oxford: Blackwell Scientific Publication, 1989. Higgins 2011 Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1 [updated March 2011]. The Cochrane Collaboration, 2011. Available from www.cochrane-handbook.org 2011.

Phebus 1988 Phebus CK, Maciak BJ, Gloninger MF, Paul HS. Zinc status of children with sickle cell anaemia: relationship to poor growth. American Journal of Hematology 1988;29(2): 67–73. Prasad 1965 Prasad AS, Diwany M, Gabr M, Sandstead HH, Mokhtar N, Hifney AE. Biochemical studies in thalassemia. Annals of Internal Medicine 1965;62:87–96. Prasad 1966 Prasad AS. Metabolism of zinc and its deficiency in human subjects. Zinc Metabolism. Springfield: Charles C. Thomas, 1966:250–303. Prasad 1983b Prasad AS. Clinical, Biochemical And Nutritional Spectrum Of Zinc Deficiency In Human Subjects: An Update. Nutrition Reviews 1983;41(7):197–208. Prasad 1985 Prasad AS. Clinical, endocrinological and biochemical effects of zinc deficiency. Clinics in Endocrinology and Metabolism 1985;14(3):567–89. Prasad 2007 Prasad AS . The Role of Zinc in Human Health. Academy of Turkish Sciences, 2007. RDA 1989 Subcommittee on the Tenth Edition of the RDAs of the Food and Nutrition Board. Recommended Dietary Allowances. 10th Edition. Washington DC: National Academy Press, 1989. RevMan 2011 The Nordic Cochrane Centre, The Cochrane Collaboration. Review Manager (RevMan). 5.1. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2011. Stewart 2007 Stewart KB, EmeryJ, Metcalfe S. Genetics in Family Medicine. 1st Edition. Australia: The Australian Government Agency Biotechnology, 2007. Thomas 2006 Thomas RE, Perera R. School-based programmes for preventing smoking. Cochrane Database of Systematic Reviews 2006, Issue 3. [DOI: 10.1002/ 14651858.CD001293.pub2] Tracey 2005 Johnston TA. Haemoglobinopathies in pregnancy. The Obstetrician & Gynaecologist 2005;7(3):149–57.

Mahyar 2010 Mahyar A. Zinc and copper status in children with betathalassemia major. Iranian Journal of Pediatrics 2010;20(3): 297–302.

WHO 1989 World Health Organization. Guidelines for the control of haemoglobin disorders. Report of the VIth Annual Meeting of the WHO working Group on Haemoglobinopathies, Cagliari, Sardinia 8–9 April 1989.

Nagalla 2010 Nagalla S, Ballas SK. Drugs for preventing red blood cell dehydration in people with sickle cell disease. Cochrane Database of Systematic Reviews 2010, Issue 1. [DOI: 10.1002/14651858.CD003426.pub3]

WHO 2006 WHO Secretariat. Thalassaemia and other haemoglobinopathies. http://apps.who.int/gb/ebwha/ pdf˙files/EB118/B118˙5-en.pdf (accessed 11 February 2011).


15

∗

Indicates the major publication for the study

CHARACTERISTICS OF STUDIES

Characteristics of included studies [ordered by study ID] Acrasoy 1987 Methods

RCT. Parallel design.

Participants

32 thalassaemia patients (19 female and 13 male). Age (1 - 18 years).

Interventions

Zinc acetate supplementation (n = 21 patients with blood transfusion): elemental zinc age-dependent doses: 22.5 mg - 45 mg for ages 1 - 4 years; 67.5 mg for ages 4 - 10 years; and 90 mg for aged over 10 years Control group (n = 11 patients): no zinc supplementation.

Outcomes

Linear growth of the patient.

Notes Risk of bias Bias

Authors’ judgement

Support for judgement

Random sequence generation (selection Unclear risk bias)

Quote: “Randomly selected the patients......”. Did not describe the method of randomisation.

Allocation concealment (selection bias)

Unclear risk

Not mentioned.

Incomplete outcome data (attrition bias) All outcomes

Low risk

All 32 participants completed study.

Selective reporting (reporting bias)

Low risk

All the outcomes were reported.

Other bias

Unclear risk

Not mentioned.

Blinding of participants and personnel Unclear risk (performance bias) All outcomes

Not mentioned.

Blinding of outcome assessment (detection Unclear risk bias) All outcomes

Not mentioned.


16

Bao 2008 Methods


Participants

36 ambulatory SCD adult patients (homozygous) (11 male and 7 female in each group) Age (18 - 47 years). Exclusion criteria were as follows: 1. nonambulatory; 2. receiving more than 6 transfusions per year or taking hydroxyurea; 3. history of substance abuse; 4. neurological or psychiatric deficits that could affect compliance; 5. use of immunosuppressive drugs; 6. patients who were positive for HIV; and 7. patients who were positive for hepatitis B.

Interventions

Zinc acetate supplementation (n = 18): 25 mg zinc acetate orally 3 times a day for 3 months Control group (n = 18): placebo.

Outcomes

Infection, vaso-occlusive pain crisis.





All patients were randomly divided into 2 groups. Did not describe the method of randomization.


Unclear risk

Allocation concealment was not described.


Low risk

All participants completed study.


Low risk

All outcomes stated in methods section reported in results.

Other bias

Unclear risk

Not discussed.

Blinding of participants and personnel Low risk (performance bias) All outcomes

Zinc-supplemented or placebo groups in pairs by the technician’s blinded choice of 1 of 2 identical bottles labelled as study drug, not labelled as zinc or as placebo (one contained zinc pills, and the other contained placebo pills)

Blinding of outcome assessment (detection Low risk bias) All outcomes

Techinicians were blinded.


17

Gupta 1995 Methods


Participants

145 participants randomised, but 15 lost to follow-up, so data for 130 participants presented (intervention group 46 males and 19 females; control group 50 males and 15 females) Age (intervention group 12 - 27 years (mean 16.4 years); control group 14 - 19 years (mean 18 years)) Inclusion criteria: Age more than 5 years with SS disease confirmed by Hb electrophoresis Exclusion criteria: Patients with chronic persistent infection

Interventions

Zinc sulphate supplementation group: 220 mg zinc sulphate 3 times per day Control group: placebo. Participants were seen weekly, at follow up until 1.5 years.

Outcomes

Sickle cell crisis: vaso-constrictive mix; haemolytic sequestration; aplastic anaemia; days in hospital and working day loss




Random sequence generation (selection Low risk bias)

Patients were randomly allocated to receive zinc or placebo (using New Castle software for randomisation)


Unclear risk

Not explained.


Unclear risk

145 participants recruited,15 patients lost to follow-up and these were not accounted for in the study publication


Low risk

All outcomes stated in the methods section were reported in the results

Other bias

Unclear risk

Little information on baseline characteristics, disease severity, medical history of participants making it difficult to ensure that the groups were similar at the start of the trial


Both patients and treating physician were blinded regarding the drug being administered during the trial. The control group received placebo capsules of identical appearance 3-times-a-day. Care was otherwise the same in the both groups


Double-blinded, treating physicians were blinded. The control group received placebo capsules of identical appearance 3-timesa-day. Care was otherwise the same in the both groups


18

Prasad 1981 (1) Methods

CCT. Cross-over design.

Participants

4 participants (all male). Age (16 - 28 years) Inclusion criteria: ambulatory, stable participants with homozygous SCD

Interventions

Zinc acetate supplementation group: 15 mg oral zinc 3-times-a-day as acetate Control group: oral placebo.

Outcomes

Plasma zinc level, alkaline phosphatase in neutrophils, basal testosterone and testosterone following intravenous gonadotrophin releasing hormone (GnRH)





Not discussed.


Unclear risk

Not discussed.


Low risk

All participants completed the study.


Low risk

All outcomes stated in the methods section were reported in the results

Other bias

Unclear risk

Not discussed.


Patients were blinded as to the type of supplementation.


Endocrinologist (AA) was blinded as to the type of supplementation

Prasad 1981 (2) Methods

CCT. Parallel design.

Participants

14 participants (all male, 7 in each group). Age (16 - 28 years). Inclusion criteria: ambulatory, stable participants with homozygous sickle cell disease between ages of


19

Prasad 1981 (2)

(Continued)

Interventions

Zinc supplementation group: 15 mg oral zinc 3 times a day as acetate Control group: oral placebo.

Outcomes

Plasma zinc level, alkaline phosphatase in neutrophils, basal testosterone and testosterone following intravenous gonadotrophin releasing hormone (GnRH)





Not discussed.


Unclear risk

Not discussed.


Low risk

All participants completed the study.


Low risk


Other bias

Unclear risk

Not discussed.


The study was conducted in a double-blind fashion. Patients were blinded as to the type of supplementation


The study was conducted in a double-blind fashion. Endocrinologist (AA) was blinded as to the type of supplementation

Prasad 1999 Methods


Participants

32 SCD participants who were divided in three groups (16 males and 16 females): Group A (n = 11) and B (n = 10) were zinc deficient based on cellular zinc criteria and Group C (n = 11) were zinc sufficient Age (19 - 49 years).

Interventions

Zinc supplementation group A: Group A participants were observed for 1 year (baseline) , following which they received zinc acetate (50 to 75 mg of elemental zinc orally daily) for 3 years Zinc supplementation group B: Group B participants were observed for 1 year (baseline) , following which they received placebo for 1 year and then switched to zinc supplementation (50 to 75 mg of elemental zinc orally daily) for 2 years Control group: Group C participants did not receive any intervention in as much as


20

Prasad 1999

(Continued)

they were zinc sufficient Outcomes

Lymphocyte and granulocyte zinc, change in interleukin-2 production, incidence of infections, number of hospitalizations and number of vaso-occlusive pain crises





Not mentioned.


Unclear risk

Not mentioned.


Low risk

All 32 participants completed the study.


Unclear risk

Outcomes are not clearly mentioned.

Other bias

Unclear risk

Not mentioned.


Not mentioned.


Not mentioned.

Rashidi 2011 Methods


Participants

120 beta thalassaemia patients (57 males and 63 females). Age (older than 18 years, mean (SD) 21.1 (9.7) years; males mean (SD) 21.6 (3.8) years and females mean (SD) 22.2 (4.6) years)

Interventions

Zinc supplement group (n = 40): 220 mg zinc sulphate containing 50 mg zinc daily for 3 months Vitamin E supplement group (n = 40): 400 mg vitamin E daily for 3 months Zinc supplement with vitamin E supplement (n = 40): similar doses and duration to previous supplement groups Control group: no supplements.

Outcomes

The effect of supplementations on serum zinc and vitamin E, SOD, GPX, TAC and BMI


21

Rashidi 2011

(Continued)





The patients were randomly assigned into 4 groups with 30 participants in each group using a random allocation method. (Random allocation method was a random permuted block or block balanced randomisation using 8 characters blocks containing A, B, C and D)


Unclear risk

Not discussed.


Low risk

120 participants completed study.


Low risk


Other bias

Unclear risk

Not discussed.


“Double-blinded RCT.”


Not discussed.

Serjeant 1970 Methods


Participants

34 SCD patients (16 male and 18 female). Age (not stated)

Interventions

Zinc supplementation group (n = 17): 200 mg zinc sulphate. Control group (n = 17): placebo (200 mg lactose).

Outcomes

Ulcer healing rate and serum zinc level.





22

Serjeant 1970

(Continued)

Random sequence generation (selection High risk bias)

Patients were alternatively allocated for treatment.


Unclear risk

Identical tablets were given to conceal their allocation in control or intervention group


Low risk

34 patients were included in the trial and 4 patients defaulted from the clinic during the trial (3 from zinc group; 1 from placebo group) and another one from the treatment group was excluded because a large scab overlying the ulcer area made reliable assessment of the ulcer size impossible


Low risk


Other bias

Unclear risk

Not discussed.


Neither person assessing the ulcer size knew which tablet contained zinc


Neither person assessing the ulcer size knew which tablet contained zinc

Zemel 2002 Methods


Participants

42 children with SCD-SS (22 males and 22 females). Age (4 - 10 years).

Interventions

Zinc supplementation group (n = 20): 10 mg elemental zinc acetate in 5 ml cherry syrup Control group (n = 22): 5 ml cherry syrup alone.

Outcomes

Improve linear growth and body composition.

Notes

Intervention and control prepared by the research pharmacy at CHOP

Risk of bias Bias




Randomization was stratified according to age group.


Not discussed.

Unclear risk


23

Zemel 2002

(Continued)


Low risk

42 children participated in the trial and 38 completed the study. 4 dropouts in total: 2 children moved away from the region, while 2 families refused to complete the study. All available information on all children were used in the analyses that was conducted


Low risk

All outcomes stated in methods section reported in result.

Other bias

Unclear risk

Not discussed.


Not discussed.


Not discussed.

BMI: body mass index CCT: controlled clinical trial GPX: glutathione peroxidase RCT: randomized controlled trial SCD: sickle cell disease SOD: superoxide dismutase TAC: total antioxidant capacity

Characteristics of excluded studies [ordered by study ID]

Study

Reason for exclusion

Mehdizadeh 2008

It was a matched case-control study and not a randomised controlled trial

Prasad 1975

Not a controlled trial.

Prasad 1983a

Not a controlled trial.

Tschumi 1981

Participants did not have a diagnosis of either sickle cell disease or thalassaemia


24

Characteristics of ongoing studies [ordered by study ID] NCT00459732 Trial name or title

Zinc & Bone Health in Thalassemia: The Think Zinc Study (ThinkZn)

Methods

RCT. Parallel design. Double-blind. Intention to treat analysis between the zinc and placebo groups

Participants

Enrollment: 45 thalassaemia patients.

Interventions

Dietary Supplement: Zinc Dietary Supplement: Placebo

Outcomes

Primary Outcome Measures: Change in lumbar spine BMD by DXA (Baseline to 18 Months) Change in pa spine BMD by DXA between baseline and 18 months Change in whole body BMC by DXA (Baseline to 18 Months) Secondary Outcome Measures: Osteocalcin (a marker of bone formation) Absolute change in serum osteocalcin between 0 and 18 months

Starting date

April 2006.

Contact information

Ellen B. Fung, PhD, RD ([email protected]).

Notes

Completed: February 2011.

BMC: bone mineral content BMD: bone mineral density RCT: randomised control trial


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DATA AND ANALYSES

Comparison 1. Zinc versus placebo (thalassaemia)

Outcome or subgroup title 1 Serum zinc level 1.1 At 3 months 2 Body mass index 2.1 At 3 months 3 Height velocity 3.1 At

No. of studies

No. of participants

1 1 1 1 1 1

Statistical method Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI)

Effect size Totals not selected 0.0 [0.0, 0.0] Totals not selected 0.0 [0.0, 0.0] Totals not selected 0.0 [0.0, 0.0]

Comparison 2. Zinc versus placebo (sickle cell disease)

Outcome or subgroup title 1 Haemoglobin 1.1 At 3 months 1.2 At 1 year 2 Serum zinc level 2.1 At 3 months 2.2 At 1 year 3 Serum zinc level 3.1 At 1 year 4 Body mass index 4.1 At 1 year 5 Weight 5.1 At 1 year 6 Sickle cell crisis 6.1 Zinc sulphate (at 1 year) 6.2 Zinc acetate (at 1 year) 7 Total number of infection 7.1 At 3 months 8 Total number of infection 8.1 At 1 year 9 Improvement in leg ulcer 9.1 At 6 months

No. of studies 2 1 1 3 1 2 1 1 1 1 1 1 2 1 1 1 1 1 1 1 1

No. of participants

36 35

Statistical method Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (Fixed, 95% CI) Mean Difference (Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Odds Ratio (M-H, Fixed, 95% CI) Odds Ratio (M-H, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Mean Difference (IV, Fixed, 95% CI) Odds Ratio (M-H, Fixed, 95% CI) Odds Ratio (M-H, Fixed, 95% CI)


Effect size Totals not selected 0.0 [0.0, 0.0] 0.0 [0.0, 0.0] Subtotals only 14.90 [6.94, 22.86] 20.25 [11.73, 28.77] Totals not selected 0.0 [0.0, 0.0] Totals not selected 0.0 [0.0, 0.0] Totals not selected 0.0 [0.0, 0.0] Totals not selected 0.0 [0.0, 0.0] 0.0 [0.0, 0.0] Totals not selected 0.0 [0.0, 0.0] Totals not selected 0.0 [0.0, 0.0] Totals not selected 0.0 [0.0, 0.0]

26

Analysis 1.1. Comparison 1 Zinc versus placebo (thalassaemia), Outcome 1 Serum zinc level. Review:

Zinc supplements for treating thalassaemia and sickle cell disease

Comparison: 1 Zinc versus placebo (thalassaemia) Outcome: 1 Serum zinc level

Study or subgroup

Zinc supplements

Mean Difference

Placebo

N

Mean(SD)

N

Mean(SD)

30

163.7 (145)

30

116 (85.8)

Mean Difference

IV,Fixed,95% CI

IV,Fixed,95% CI

1 At 3 months Rashidi 2011

47.70 [ -12.59, 107.99 ]

-200

-100

0

Favours placebo

100

200

Favours zinc supplements

Analysis 1.2. Comparison 1 Zinc versus placebo (thalassaemia), Outcome 2 Body mass index. Review:


Comparison: 1 Zinc versus placebo (thalassaemia) Outcome: 2 Body mass index

Study or subgroup

Zinc supplements

Mean Difference

Placebo

N

Mean(SD)

N

Mean(SD)

30

20.1 (2.7)

30

19.4 (2.2)

Mean Difference

IV,Fixed,95% CI

IV,Fixed,95% CI

1 At 3 months Rashidi 2011

0.70 [ -0.55, 1.95 ]

-4

-2

Favours placebo


0

2

4


27

Analysis 1.3. Comparison 1 Zinc versus placebo (thalassaemia), Outcome 3 Height velocity. Review:


Comparison: 1 Zinc versus placebo (thalassaemia) Outcome: 3 Height velocity

Study or subgroup

Zinc supplements

Mean Difference

Placebo

N

Mean(SD)

N

Mean(SD)

15

7.77 (1.51)

11

4.4 (1.13)

Mean Difference

IV,Fixed,95% CI

IV,Fixed,95% CI

1 At Acrasoy 1987

3.37 [ 2.36, 4.38 ]

-4

-2

0

Favours placebo

2

4


Analysis 2.1. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 1 Haemoglobin. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 1 Haemoglobin

Study or subgroup

Zinc supplements

Mean Difference

Placebo

Mean Difference

N

Mean(SD)

N

Mean(SD)

IV,Fixed,95% CI

IV,Fixed,95% CI

18

8.59 (1.38)

18

8.53 (1.38)

0.06 [ -0.84, 0.96 ]

11

8.84 (0.5)

11

8.91 (2.2)

-0.07 [ -1.40, 1.26 ]

1 At 3 months Bao 2008 2 At 1 year Prasad 1999

-4

-2

Favours placebo


0

2

4


28

Analysis 2.2. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 2 Serum zinc level. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 2 Serum zinc level

Study or subgroup

Zinc supplements

Mean Difference

Placebo

N

Mean(SD)

N

Mean(SD)

18

104.2 (15)

18

89.3 (8.5)

Weight

IV,Fixed,95% CI

Mean Difference IV,Fixed,95% CI

1 At 3 months Bao 2008

Subtotal (95% CI)

18

18

100.0 %

14.90 [ 6.94, 22.86 ]

100.0 %

14.90 [ 6.94, 22.86 ]

Heterogeneity: not applicable Test for overall effect: Z = 3.67 (P = 0.00025) 2 At 1 year Prasad 1981 (2) Prasad 1999

Subtotal (95% CI)

7

121.1 (15.6)

7

89.5 (3.5)

51.8 %

31.60 [ 19.76, 43.44 ]

11

96.72 (15)

10

88.66 (13.7)

48.2 %

8.06 [ -4.22, 20.34 ]

18

100.0 % 20.25 [ 11.73, 28.77 ]

17

Heterogeneity: Chi2 = 7.32, df = 1 (P = 0.01); I2 =86% Test for overall effect: Z = 4.66 (P < 0.00001)

-50

-25

0

Favours placebo

25

50


Analysis 2.3. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 3 Serum zinc level. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 3 Serum zinc level

Study or subgroup

Mean Difference

Mean Difference (SE)

Mean Difference

IV,Fixed,95% CI

IV,Fixed,95% CI

1 At 1 year Prasad 1981 (1)

-35 (9.67)

-35.00 [ -53.95, -16.05 ]

-100

-50



0

50

100

Favours placebo

29

Analysis 2.4. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 4 Body mass index. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 4 Body mass index

Study or subgroup

Zinc supplements

Mean Difference

Placebo

N

Mean(SD)

N

Mean(SD)

18

15 (1.1)

20

15 (2.3)

Mean Difference

IV,Fixed,95% CI

IV,Fixed,95% CI

1 At 1 year Zemel 2002

0.0 [ -1.13, 1.13 ]

-2

-1

0

Favours placebo

1

2


Analysis 2.5. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 5 Weight. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 5 Weight

Study or subgroup

Zinc supplements

Mean Difference

Placebo

N

Mean(SD)

N

Mean(SD)

18

23.5 (5)

20

25 (6.2)

Mean Difference

IV,Fixed,95% CI

IV,Fixed,95% CI

1 At 1 year Zemel 2002

-1.50 [ -5.07, 2.07 ]

-10

-5

Favours placebo


0

5

10


30

Analysis 2.6. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 6 Sickle cell crisis. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 6 Sickle cell crisis

Study or subgroup

Zinc supplements

Mean Difference

Placebo

Mean Difference

N

Mean(SD)

N

Mean(SD)

IV,Fixed,95% CI

IV,Fixed,95% CI

65

2.46 (1.04)

65

5.29 (2.58)

-2.83 [ -3.51, -2.15 ]

11

6.72 (3.6)

11

5.18 (4.8)

1.54 [ -2.01, 5.09 ]

1 Zinc sulphate (at 1 year) Gupta 1995 2 Zinc acetate (at 1 year) Prasad 1999

-10

-5

0


5

10

Favours placebo

Analysis 2.7. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 7 Total number of infection. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 7 Total number of infection

Study or subgroup

Zinc supplements

Placebo

Odds Ratio

Odds Ratio

n/N

n/N

M-H,Fixed,95% CI

M-H,Fixed,95% CI

1/18

10/18

1 At 3 months Bao 2008

0.05 [ 0.01, 0.43 ]

0.001 0.01 0.1 Favours zinc supplements


1

10 100 1000 Favours placebo

31

Analysis 2.8. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 8 Total number of infection. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 8 Total number of infection

Study or subgroup

Zinc supplements

Mean Difference

Placebo

N

Mean(SD)

N

Mean(SD)

11

0.36 (0.7)

10

8 (5.2)

Mean Difference

IV,Fixed,95% CI

IV,Fixed,95% CI

1 At 1 year Prasad 1999

-7.64 [ -10.89, -4.39 ]

-10

-5

0


5

10

Favours placebo

Analysis 2.9. Comparison 2 Zinc versus placebo (sickle cell disease), Outcome 9 Improvement in leg ulcer. Review:


Comparison: 2 Zinc versus placebo (sickle cell disease) Outcome: 9 Improvement in leg ulcer

Study or subgroup

Zinc supplements

Placebo

Odds Ratio

Odds Ratio

n/N

n/N

M-H,Fixed,95% CI

M-H,Fixed,95% CI

13/15

8/13

1 At 6 months Serjeant 1970

4.06 [ 0.63, 26.13 ]

0.01

0.1

Favours placebo


1

10

100


32

ADDITIONAL TABLES Table 1. Gupta 1995 - Types of crises

Types of crisis

Control (n = 65)

Intervention (n = 65)

Vaso-occlusive

220 (63.95%)

91 (58.87%)

Mixed

68 (19.76%)

38 (23.75%)

Haemolytic

40 (11.62%)

17 (9.37%)

Sequestration

12 (1.48%)

12 (1.25%)

Alastic

4 (1.16%)

2 (1.25%)

Total

344

160

Data represent number of events.

CONTRIBUTIONS OF AUTHORS

Preliminary database search

Dr Kye Mon, Dr Adinegara

Develop and run the search strategies

Dr Kye Mon and the Group’s Trials Search Co-ordinator performed these

Background

Dr Kye Mon, Dr Adinegara, Dr Amit, Dr Ankur Barua

Objectives

Dr Kye Mon, Dr Adinegara

Methodology

Dr Kye Mon,Dr Adinegara, Dr Amit, Dr NS Nair

DECLARATIONS OF INTEREST None known.


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