A diagnostic performance evaluation of rapid

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Okokon I. Itaa, Akaninyene A. Otub,c,*, Kenneth Onyedibed, Anthony A. Iwuafora, Edmund Banwatd and Daniel Z. Egahd a

Department of Medical Microbiology and Parasitology, University of Calabar, Calabar, Cross River State; bDepartment of Internal Medicine, University of Calabar, Calabar, Cross River State, Nigeria; cNational Aspergillosis Centre, Manchester University NHS Foundation Trust, Manchester, United Kingdom; dDepartment of Medical Microbiology and Parasitology, University of Jos, Plateau State, Nigeria

*Corresponding author: Present address: National Aspergillosis Centre, Manchester University NHS Foundation Trust, Manchester, United Kingdom. M23 9LT. Tel: +447561045554; E mail address: [email protected]

Received 7 February 2018; revised 13 May 2018; editorial decision 19 June 2018; accepted 19 June 2018 Background: Rapid diagnostic tests are frequently used in healthcare settings across Nigeria for diagnosis of Plasmodium falciparum malaria, which is the commonest form of malaria in the country. In this study, the performance of a rapid diagnostic test (RDT) was compared with expert microscopy using the polymerase chain reaction (PCR) as the reference standard in a tertiary hospital in Jos, Nigeria. Methods: This study was a prospective, cross-sectional, hospital-based study. A total of 200 participants of all ages presenting to Jos University Teaching Hospital with a history of fever or an axillary temperature of >37.5°C were recruited. Blood specimens were collected and malaria testing was done using RDT, microscopy and PCR. Results: The prevalence of malaria in this study was 17%, 15% and 13% by PCR, microscopy and RDT, respectively. Compared with microscopy, RDT had lower sensitivity of 75% (95% CI: 56.60–88.54) vs 88.24% (95% CI: 72.55–96.70), lower specificity of 98.80% (95% CI: 95.72–99.85) vs 100.0% (95% CI: 97.80–100.0), lower positive predictive value 92.31 (95% CI: 74.89–97.97) vs 100 (95% CI: 98.0–100.0), and lower negative predictive value 95.35 (95% CI: 91.83–97.39) versus 97.65 (95% CI: 94.30–99.05). Conclusion: The diagnostic performance of expert microscopy was better than RDT in the diagnosis of Plasmodium falciparum malaria. Quality assurance procedures such as using expert microscopy to cross-check a proportion of RDT negative results in patients with clinical features of malaria is desirable. Keywords: Jos, malaria, Nigeria, malaria microscopy, polymerase chain reaction, rapid diagnostic test

Introduction Global estimates reflect a decrease in the number of malaria cases from 237 million in 2010 to 216 million cases in 20161 although there has been no appreciable decrease in the estimated number of malaria cases between 2015 and 2016. The global mortality rates from malaria have remained essentially the same as there were an estimated 446 000 in 2015 compared with about 445 000 in 2016.1 About 3.2 billion people remain at risk of malaria and malaria still causes an unacceptably high number of deaths in children under the age of five.2 Approximately 80% of malaria deaths are concentrated in just

15 countries, all of which are in sub-Saharan Africa except for India.1 In Nigeria, malaria is responsible for 60% of outpatient visits to health facilities, 30% of childhood deaths of children under 1 year and 11% of maternal deaths.3 Approximately 20% of hospital admissions and 10% of hospital deaths in Nigeria have been attributed to malaria.4 This makes early and accurate diagnosis of malaria absolutely imperative. Diagnosing malaria based on clinical findings alone leads to over-diagnosis, overtreatment, delay in seeking an alternative diagnosis in parasite negative patients, drug wastage, exposure of malaria-free patients to anti-malarials with their associated side effects and creates selective pressure for drug resistance.5,6 However,

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A diagnostic performance evaluation of rapid diagnostic tests and microscopy for malaria diagnosis using nested polymerase chain reaction as reference standard in a tertiary hospital in Jos, Nigeria

ORIGINAL ARTICLE

Trans R Soc Trop Med Hyg 2018; 00: 1–7 doi:10.1093/trstmh/try071

O. I. Ita et al.

outpatients of both sexes referred to the Microbiology Department for malaria microscopy. Patients of all ages with a history of fever or axillary temperature of >37.5°C were included, while any patient on anti-malarial treatment or who had received anti-malarial therapy in the 2 weeks preceding the study was excluded from the study. The sampling of participants was done consecutively as defined by the inclusion criteria. During the study period, a total of 620 patients were referred for malaria parasite testing and 550 of them were approached to participate in the study.

Sample size calculation The minimum sample size was calculated using a Jos malaria prevalence of 13% and a 5% significance. The calculated minimum was 174 which including 10% for invalid samples came to 192. A total of 200 eligible subjects were eventually recruited (see Figure 2). Out of the 350 who were not recruited, 250 of them had taken antimalarials before presenting to hospital and were not febrile at the time of presentation. Seventy of the 350 patients who were not recruited were inpatients on antimalarials and 10 patients were afebrile. Ten patients did not give their consent to participate. The team for this project consisted of university graduates of laboratory medicine. All team members received a 2-week

Material and methods Study area Participants were recruited from Jos University Teaching Hospital from October 2012 to March 2013. Jos is located at 9°56’N 8°53’E/9.933°N 8.883°E (see Figure 1). Its altitude ranges from 1238 m above sea level to 1829 m.22 Its overall average relative humidity is 55%. Its average monthly temperatures range from 17°C to 29°C from mid-November to late January with a night time temperature drop as low as 11°C, resulting in chilly nights. The city of Jos receives about 1400 mm (55.1 inches) of rainfall annually with July to September being the months with the highest rainfall. The average rainfall during the months of October to March is 13.3 mm.22 Plasmodium falciparum is the predominant malaria species in this area, although a study by Uneke and colleagues showed mixed infections of Plasmodium falciparum and Plasmodium malariae occurring in 2.6% of cases.23

Study design This study was a hospital-based, cross-sectional study carried out over a 3-month period. Demographic and clinical data were collected from the patients by means of a structured questionnaire. The study population was made up of inpatients and

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Figure 1. Map of Nigeria showing the location of the study area; Jos, Plateau State. Courtesy: The Nigerian Times.24

620 referred for malaria testing

550 approached to participate in study

200 eligible participants recruited

Figure 2. Schematic showing the recruitment process.

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presumptive treatment of malaria without laboratory confirmation is commonplace in Nigerian health facilities.7,8 The diagnosis of malaria is based on laboratory methods. Microscopic examination of stained thick and thin smears is traditionally the ‘gold standard’ for malaria diagnosis.9 Expert microscopy utilizes thick blood smears to identify parasitaemia, while thin smears are used for speciation, quantification of parasitaemia and evaluation of parasite morphology at a higher magnification.10 However, this technique requires trained microscopists and is time-consuming. The challenges of providing malaria microscopy services in resource-constrained settings include lack of high quality equipment, erratic power supply, the use of low quality reagents and a lack of supervision in health centres.11 Rapid blood tests (RDT) for malaria are commercially available in many settings in sub-Saharan Africa. These tests require little training, are easy to use, provide rapid results, do not require electricity or the use of stains, and are subject to less investigator-related variation compared with microscopy.12,13 The World Health Organization (WHO) has recognized RDT as a solution to improve malaria diagnosis.12 The polymerase chain reaction (PCR) for malaria diagnosis is considered to be more sensitive and specific than other tests, detecting as few as 5–10 parasites per μL of blood.14–20 More recent routine PCR can now often detect

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