Death by mental retardation? - Wiley Online Library

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Journal of Intellectual Disability Research 1183

doi: 10.1111/j.1365-2788.2012.01614.x

volume 57 part 12 pp 1183–1190 december 2013

Brief report

Death by mental retardation? The influence of ambiguity on death certificate coding error for adults with intellectual disability S. D. Landes & C.W. Peek Department of Sociology and Criminology & Law, University of Florida, Gainesville, Florida, USA

Abstract Background Although the coding of mental retardation as underlying cause of death has been recognised by previous researchers as erroneous, factors influencing this inaccuracy have not been sufficiently analysed. This study explores the effects of diagnostic ambiguity on risk of mental retardation being coded as underlying cause of death on US death certificates from 2004. Methods Utilising all US death certificates from 2004 that included a cause of death code for mental retardation, logistic regression analysis provided estimates of the likelihood of having mental retardation erroneously coded as the underlying cause of death. Estimators used to measure ambiguity included the number of multiple causes of death, the place of death, and ICD-10 diagnostic Chapter codes. Results A total of 2278 US death certificates from 2004 included a cause of death code for mental retardation. Of these death certificates, 20% erroneously coded mental retardation as the underlying cause of death. Reflecting the negative impact of diagnostic ambiguity on death certificate coding Correspondence: Mr Scott D. Landes, Department of Sociology and Criminology & Law, University of Florida, Gainesville, FL 32611-7330, USA (e-mail: [email protected]).

accuracy, mental retardation was more likely to be coded as underlying cause of death for decedents who: (1) had a death certificate that provided less information on co-morbid disease processes; (2) died in an outpatient or emergency room setting; or (3) had either abnormal symptomatology or death by injury, accident or other external cause. Conclusions Findings from this study, as well as prior research, demonstrate that attempts to understand mortality trends for this population must attend to frequent underlying cause of death coding errors which threaten accuracy of cause of death data. Furthermore, inquiry is warranted into the impetus behind US death certificate coding policy that continues to allow the erroneous coding of ‘death by mental retardation’. Keywords cause of death, death certificate, health disparity, intellectual disability, mortality

Introduction Although mental retardation1 was historically considered a disease process, more recent thought 1 While the term ‘intellectual disability’ will be utilised throughout this paper, ‘mental retardation’ is the diagnosis category on US death certificates and will be included when needed to accurately describe data.

© 2012 The Authors. Journal of Intellectual Disability Research © 2012 John Wiley & Sons Ltd, MENCAP & IASSID

volume 57 part 12 december 2013

Journal of Intellectual Disability Research 1184 S. D. Landes & C. W. Peek • Death by mental retardation?

accurately identifies this diagnosis as a disability (Luckasson et al. 2002; Ouellette-Kuntz et al. 2005). Despite this advance in understanding, the diagnosis of mental retardation is still routinely identified as the underlying cause of death on US death certificates. This type of death certificate coding error may simply be the result of a lack of physician training on death certificate completion (Messite & Stellman 1996; Goodin & Hanzlick 1997; Lenfant & Thom 1998; Myers & Farquhar 1998). However, in light of prior research detailing an increased level of under-diagnosis and misdiagnosis of chronic illness among individuals with intellectual disability (ID) because of healthcare disparities (Ouellette-Kuntz 2005; Scheepers et al. 2005; Krahn et al. 2006), these death certificate errors may be the result of increased diagnostic ambiguity surrounding the often inadequate medical histories of decedents with ID. For all known decedents in the USA, an official death certificate is completed by a certifying physician, coroner or medical examiner immediately following death (Dimick 2009). The death certificate includes personal information, basic demographic information (age, gender, educational level, race), as well as cause of death information for the decedent. The cause of death information records the sequential chain of events leading to death, beginning with the underlying cause of death and leading to the immediate cause of death, as well as other disease processes contributing to death but not directly related to the cause of death. According the World Health Organisation rules for coding the death certificate, the underlying cause of death is defined as the ‘(a) disease or injury which initiated the train of morbid events leading directly to death, or (b) the circumstances of the accident or violence which produced the fatal injury’ (World Health Organisation 1975). Prior research on the death certificate coding explains that ID does not cause death and should not be identified as the underlying cause of death (Baird & Sadovnick 1990; Tyrer & Mcgrother 2009). The continued use of mental retardation as an underlying cause of death diagnosis may result from ambiguity surrounding the medical history of the decedent (Baird & Sadovnick 1990) or uncertainty regarding the proper location in which to record ID on the death certificate (Tyrer &

Mcgrother 2009). The aim of this paper was to analyse the influence of ambiguity on the erroneous coding of mental retardation as underlying cause of death in US death certificates from 2004. A secondary aim was to highlight the potential impact of this coding error on mortality data for this population and the need to further explore US death certificate coding instructions for ID.

Methods Population The data used for this study were from The Multiple Cause of Death Public Use File for 2004, which provided data on all recorded deaths in the USA during 2004 (U.S. Deptartment of Health and Human Services National Center for Health Statistics 2004). The unit of analysis for this data set was the US Standard Certificate of Death which included information for each decedent on underlying cause of death, multiple causes of death, place of death, manner of death, whether an autopsy was performed, month and day of the week of death, sex, race, age, marital status, and education. The population frame utilised for this study consisted of all deaths recorded in the USA during 2004 (n = 2 452 506).

Procedure All adults aged 21 or over that had mental retardation recorded as either the underlying cause of death or a multiple cause of death were identified. As such, this study only analysed death certificate data for individuals who had an ID recorded on the death certificate and did not include decedents who did not have ID recorded on their death certificate. Basic social demographics of age, race and educational attainment were included in analysis. As 88% of decedents were white, race was captured with a dichotomous variable measuring white (coded 1) and other (coded 0). Ambiguity was conceptualised using measures for multiple causes of death, place of death, and specific ICD-10 (International Classification of Disease) diagnosis categories. Following the lead of previous research (Manton 1980; Wall et al. 2005), the multiple causes of death variable measured




adequacy/inadequacy of disease information present to the physician at the time of death by calculating the number of diagnoses listed on the death certificate beyond the underlying cause of death. As such, a lower number of multiple causes of death reflected increased ambiguity regarding the decedent’s medical history and an increased likelihood of coding error (Lenfant & Thom 1998; Wall et al. 2005). Place of death measured possible ambiguity regarding the availability of the decedent’s documented disease history. When compared with an inpatient or nursing home setting, locations such as an emergency room or outpatient clinic were less likely to have thorough medical information available on the decedent (Wall et al. 2005). Variation in diagnostic ambiguity corresponding to place of death was analysed by comparing the percent of erroneous coding of deaths that occurred in (1) emergency rooms or outpatient clinics; (2) a hospital inpatient settings; (3) nursing homes; (4) homes; or (5) other setting. Building on Lenfant & Thom’s (1998) contention that those with an accurately characterised illness are less likely to have death certificate coding errors, the focus for this study was on the ICD-10 Chapter for Symptoms, signs, and abnormal clinical and laboratory findings, which measured diagnostic ambiguity. According to the World Health Organisation’s description, diagnoses falling under this Chapter code are used by the certifying physician when the decedent’s actual medical symptoms or clinical findings were not fully understood because the decedent did not have proper diagnostic care prior to death, problems with medical care prior to death, or the cause of death simply could not be properly identified (World Health Organisation 1992). Accordingly, this variable was coded 1 for decedents who had a diagnosis captured by Symptoms, signs, and abnormal clinical and laboratory findings listed anywhere on their death certificate; otherwise it was coded 0. To compare the effects of this ICD-10 Chapter describing ambiguous diagnoses to less ambiguous diagnoses, dichotomous variables were also included for all other ICD-10 Chapter codes identified on over 10% of the death certificates included in the study. Each included ICD-10 Chapter code dichotomous variable was coded 1 when the decedent had a diagno-

sis captured within the particular Chapter code anywhere on the death certificate, and 0 if a diagnosis from the Chapter code was not assigned.

Results Bivariate analysis The selected population included all 2278 adult decedents, aged 21 or over, who had mental retardation listed as a cause of death. Twenty per cent of death certificates had mental retardation erroneously coded as the underlying cause of death (SD = 0.40), which will hereby simply be referred to as ‘coding error’. Bivariate correlation revealed a significant negative correlation between the number of multiple causes of death (M = 3.37, SD = 1.71) and coding error (r = -0.18, n = 2278, P < 0.01). A t-test confirmed that those who had this coding error had a lower mean number of multiple causes of death (M = 2.70, SD = 1.50) than those who did not (M = 3.48, SD = 1.72), t(2276) = 8.86, P < 0.01. Though the table is not included in this paper, crosstabulation analysis demonstrated that death certificates with 1–3 listed multiple causes of death were more likely to have coding error, while death certificates with 4–16 listed multiple causes of death were less likely to have coding error c2(12, n = 2778) = 113.34, P < 0.01 (analysis available from the authors upon request). Mean age for the population was 60 years (SD = 16.83) with a range of 21–103 years. While there was not a significant correlation between age and number of multiple causes of death, age was also negatively correlated with coding error, with older age associated with less coding error (r = -0.18, n = 2278, P < 0.01). Bivariate crosstabulation of dichotomous variables clarified that mean coding error differences were not significant for gender or race. However, as reported in Table 1, coding error differences did vary significantly across place of death. Decedents who died in an emergency room or outpatient clinic were more likely to have coding error compared with any other location. Those who had an ambiguous diagnosis, identified by the ICD-10 Chapter ‘Symptoms, signs and abnormal clinical and laboratory findings’, or an external cause of death, identified by the ICD-10 Chapter ‘Injury, poisoning and certain other consequences of external causes’, were more likely to




Table 1 Crosstabulations of erroneous coding with dichotomous independent variables

Erroneous coding

Female

No Yes No Yes

White Place of death Outpatient or ER Hospital inpatient Nursing home Home Other Mentioned causes of death Symptoms, signs and abnormal clinical and laboratory findings Certain infectious and parasitic diseases Neoplasms Endocrine, nutritional and metabolic diseases Diseases of the nervous system Diseases of the circulatory system Diseases of the respiratory system Diseases of the digestive system Diseases of the genitourinary system Injury, poisoning and certain other consequences of external causes

No Yes No Yes No Yes No Yes No Yes No Yes No Yes No Yes No Yes No Yes

No (%)

Yes (%)

980 (78.9) 840 (81.1) 227 (80.2) 1593 (79.8)

262 (21.1) 196 (18.9) 56 (19.8) 402 (20.2)

129 (66.2) 687 (80.0) 662 (81.9) 224 (82.7) 118 (81.4) 1200 (83.2) 620 (74.2) 1573 (78.9) 247 (87.0) 1586 (77.9) 234 (97.1) 1458 (77.9) 362 (88.9) 1380 (77.2) 440 (89.6) 916 (74.4) 904 (86.4) 982 (79.3) 838 (80.7) 1571 (78.3) 249 (91.5) 1597 (78.9) 223 (87.8) 1694 (82.7) 126 (55.0)

c2

M (SD)

1.67

0.45 (0.50)

0.02

0.88 (0.33)

66 (33.8) 172 (20.0) 146 (18.1) 47 (17.3) 27 (18.6)

26.50**

0.09 (0.28) 0.38 (0.49) 0.35 (0.48) 0.12 (0.33) 0.06 (0.24)

242 (16.8) 216 (25.8) 421 (21.1) 37 (13.0) 451 (22.1) 7 (2.9) 413 (22.1) 45 (11.1) 407 (22.8) 51 (10.4) 316 (25.6) 142 (13.6) 257 (20.7) 201 (19.3) 435 (21.7) 23 (8.5) 427 (21.1) 31 (12.2) 355 (17.3) 103 (45.0)

27.01**

0.37 (0.48)

10.12**

0.12 (0.33)

49.64**

0.11 (0.31)

25.26**

0.18 (0.38)

36.80**

0.22 (0.41)

51.34**

0.46 (0.50)

0.69

0.46 (0.50)

26.10**

0.12 (0.32)

11.11**

0.11 (0.32)

98.06**

0.10 (0.30)

* P < 0.05, ** P < 0.01, n = 2278; percentages shown in parentheses are row percentages. df = 4 for Place of death and df = 1 for all other crosstabulations.

have coding error. In contrast, decedents with any of the following less ambiguous ICD-10 Chapter diagnoses were less likely to have coding error: Neoplasms; Endocrine, nutritional and metabolic diseases; Diseases of the nervous system; Diseases of the circulatory system; Diseases of the digestive system; Diseases of the genitourinary system. Mean coding error differences for those with and without a diagnosis falling in the ICD-10 Chapter for Diseases of the respiratory system were not significant.

Regression analysis As reported in Table 2, based on logistic regression analysis, each model was significant at the P < 0.01 level and model fit increased when place of death and ICD-10 Chapter codes were added to number of multiple causes of death. Age was significant for a negative relationship with coding error in all models. Controlling for all other variables, with each year increase in age, decedents were 1% less likely to have coding error. Coding error decreased




Table 2 Logistic regression of mental retardation as underlying cause of death on number of multiple causes of death, place of death, and mentioned causes

Model 1

Model 2

Variable

b

eb

(SE)

Constant Social demographics Age Female White Number of multiple causes of death Place of death Outpatient/ER (ref) Hospital inpatient Nursing home Home Other Mentioned cause of death Symptoms, signs and abnormal clinical and laboratory findings Certain infectious and parasitic diseases Neoplasms Endocrine, nutritional and metabolic diseases Diseases of the nervous system Diseases of the circulatory system Diseases of the respiratory system Diseases of the digestive system Diseases of the genitourinary system Injury, poisoning and certain other consequences of external causes

-0.37

1.44

(0.25)

-0.01** -0.08 0.15 -0.33**

0.97 0.92 1.16 0.72

(0.00) (0.11) (0.17) (0.04)

-2 Log likelihood Cox & Snell pseudo R2 c2 df

2179.05 0.05 107.42** 4

Model 3 eb

(SE)

0.90**

2.46

(0.28)

-0.01** -0.06 0.18 -0.34**

0.99 0.94 1.20 0.71

-0.58** -0.69** -0.99** -0.75**

0.56 0.50 0.37 0.47

b

2158.10 0.06 128.37** 8

eb

(SE)

0.94**

2.55

(0.32)

(0.00) (0.11) (0.18) (0.04)

-0.01** 0.06 0.17 -0.51**

0.99 1.06 1.19 0.60

(0.00) (0.12) (0.18) (0.07)

(0.18) (0.19) (0.23) (0.27)

-0.37 -0.61* -0.74** -0.94**

0.70 0.60 0.48 0.39

(0.21) (0.22) (0.27) (0.31)

1.03**

2.81

(0.14)

-0.25 -2.30** -0.19 -0.99** -0.40* -0.02 -0.95** -0.10 2.21**

0.77 0.10 0.83 0.37 0.67 0.98 0.39 0.91 9.13

(0.22) (0.41) (0.20) (0.17) (0.16) (0.15) (0.26) (0.23) (0.23)

b

1816.00 0.19 470.47** 18

* P < 0.05, ** P < 0.01; n = 2278 for all models.

as the number of multiple causes of death increased. The effects of this relationship strengthened with the addition of place of death and the ICD-10 Chapter codes, with the final model demonstrating that each unit increase in number of multiple causes of death recorded decreased the odds ratio of coding error by 40%. Adults with ID that died in an emergency room or outpatient setting, were more likely to have coding error than those who died in a hospital inpatient setting, nursing home, at home, or other site. While maintaining significance, the coding error differential narrowed between dying in an emergency room or outpatient setting and dying in a

nursing home or home with the addition of the ICD-10 codes, while the differential between the effects of death in an emergency room or outpatient setting and ‘other’ setting widened. Also, the likelihood of having coding error when dying in an emergency room or outpatient setting as compared with a hospital inpatient setting was no longer significant when holding the ICD-10 Chapter code information constant. Ill-defined, ambiguous diagnoses as reflected in ICD-10 Chapter codes also predicted coding error. Decedents who had a diagnosis code for Symptoms, signs and abnormal clinical and laboratory findings were more likely to have coding error than those


Journal of Intellectual Disability Research


1188 S. D. Landes & C. W. Peek • Death by mental retardation?

who did not. According to Model 3, the odds ratio for having coding error for those decedents who had an ICD-10 code representing diagnostic ambiguity was 2.85 times more likely than for those who did not have a diagnosis code representing diagnostic ambiguity. In comparison decedents who had a diagnosis falling under less ambiguous diagnostic codes, such as Neoplasms, Diseases of the nervous system, Diseases of the circulatory system, or Diseases of the digestive system were less likely to have coding error. While still reporting an inverse effect on coding error, ICD-10 Chapter variables for Certain infections and parasitic diseases, Endocrine, nutritional and metabolic disease, Diseases of the respiratory system, and Disease of the genitourinary system were not significant. One of the ICD-10 Chapter variables measures representing increased diagnostic accuracy was significant for a positive relationship with coding error. According to Model 3, the odds ratio of having coding error for those with Injury, poisoning, and certain other consequences of external causes was 9.46 times more likely than for those who did not have a diagnosis in this area.

Discussion While true that coding errors on the death certificates may partially be explained by a lack of proper training for physicians on death certificate completion, findings from this study indicate that contextual factors also influenced the accuracy of death certificates of individuals with ID. In the midst of ambiguity regarding disease history and diagnosis, certifying physicians were more likely to engage in diagnostic overshadowing, or to erroneously code a more recognisable and less ambiguous condition, mental retardation, as the underlying cause of death (Baird & Sadovnick 1990; Tyrer & Mcgrother 2009). Understanding a lower number of multiple causes of death as indicative of ambiguity regarding disease history (Wall et al. 2005), decedents who had less multiple causes of death listed on their death certificate, reflecting decreased documentation of their medical history, were more likely to have coding error. Furthermore, results from this study confirmed that adults with ID who died in a location with the least likelihood of having thorough

documentation of medical history on site, such as an emergency room or outpatient clinic (Wall et al. 2005), were at greater risk of erroneous coding than those dying in other locations. Supporting Baird & Sadovnick’s (1990) research, results from this study also show that when a general ambiguity from inadequate medical information is accompanied by further diagnostic ambiguity, the chances of coding error increased dramatically. Decedents who had an ambiguous diagnosis, abnormal symptomatology, listed anywhere on the death certificate were much more likely to have coding error. In comparison, decedents who had adequate, less ambiguous and often long-term diagnoses such as cancer, epilepsy, heart disease, and intestinal disease were less likely to have coding error. Results were not significant for other less ambiguous disease processes more indicative of sudden onset and short-term duration such as septicaemia, volume depletion, pneumonia, or urinary tract infections. Interestingly, those decedents who died of injury, poisoning, or other external causes were also more likely to have coding error, possibly because of the general ambiguity often surrounding accidental deaths. This would appear true in this population as one of the frequently listed diagnoses in this category was ‘Foreign body in respiratory tract, part unspecified’. Age did prove to influence whether the decedent had coding error. And while further research is needed to confirm this contention, it is likely this is a reflection that older adults tend to have a higher frequency of chronic illness(es), and decedents with documented chronic illness(es) are less likely to have death certificate coding error (Wall et al. 2005). These findings not only demonstrate the influence of ambiguity on death certificate coding errors, they also identify a concern regarding the development of public health agendas for persons with ID. Death certificates provide vital data that aid in understanding morbidity and mortality trends as well as the prevalence and trajectory of diseases within specific populations (Israel et al. 1986; Messite & Stellman 1996; Lloyd-Jones et al. 1998; Patja et al. 2001). In turn, interpretation of these trends is used to shape public health policy and agendas which inform research, prevention, and programme development needed to improve health-




care outcomes (Hoel et al. 1993; Rogers 1995; Davis 1997; Hayden 1998). Therefore, death certificate coding errors can hamper efforts to enact accurately informed public healthcare policy (Hoel et al. 1993; Lloyd-Jones et al. 1998). Another concern that is named, but not fully explored in data analysis is the continued allowance of utilising mental retardation as a possible underlying cause of death when the certifying physician does not know the actual underlying cause of death. Death certificate coding instructions clarify that mental retardation is allowed to be used as an underlying cause of death when the certifying physician does not know the actual underlying cause of death. Instructions for coding mental retardation as underlying cause of death read, ‘Not to be used if the underlying physical condition is known’ (National Center for Health Statistics 2011). The question remains, why at any time is a physician allowed to utilise a diagnosis code for a disability as an underlying cause of death, which represents a disease, injury, accident, or act of violence? As Tyrer & McGrother (2009) argue, there is a valid place for recording ID on the death certificate, but not as underlying cause of death. For US death certificates, it seems that including ID under section 32, Part II, which allows for ‘other significant conditions contributing to death but not resulting in the underlying cause’ (National Center for Health Statistics 2011) would allow this disability to be accurately recorded without erroneously identifying it as a cause of death. Findings from this study suggest the possibility that health inequalities experienced by individuals with ID during their lifetimes (Graham 2005; Krahn et al. 2006; Emerson 2007) carry forth into death certificate coding and mortality data for this population. As Ouellette-Kuntz (2005) explains, healthcare disparities experienced by individuals with ID often result in under-diagnosis of co-morbid disease processes and diagnostic overshadowing, as ID is often incorrectly identified as the cause of health problems. Though in need of further research for clarification, results from this study suggest a similar trend after death, with ID diagnostically overshadowing the true cause of death on US death certificates. Findings support the need to clarify proper usage of ID diagnoses on US death certificates in order to ensure accurate information regarding

underlying cause of death data for this population, and the need for additional research into the effect of lifetime health disparities on mortality coding for individuals with ID.

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Accepted 25 July 2012
