Original ArticleComorbidity information in older patients at an emergency visit: self-report vs. administrative data had poor agreement but similar predictive validity
Introduction
In 1987, Charlson et al. published and validated a weighted chart-based comorbidity index whose purpose was to predict 1-year mortality and quantify the chronic disease load in patients participating in therapeutic trials [1]. The Charlson Comorbidity Index (CCI) became widely used in epidemiologic studies to simplify data analysis [2] and has been used in targeted clinical interventions [3].
Because of the high cost of medical chart reviews [3] and increasing reliance of patients on outpatient care [4], the original CCI has since been adapted for use with hospital administrative data [5], [6] and medical claims data [7]. Cost-efficient self-report comorbidity scales [8] have also been developed; one such scale predicted 1-year mortality comparably to a comorbidity index based on administrative data [9]. To our knowledge, however, no study has yet compared self-report and administrative data in an emergency setting. Both data sources have potential limitations: self-report data suffer from recall bias, and administrative data are limited by diagnostic and coding errors.
Older emergency department (ED) patients have a high number of ED visits, high risk of adverse outcomes [10], and poor accuracy of ED diagnoses [11], [12]. Comorbidity indices, however, do not appear to perform as well among elders, a population with a high comorbidity burden [13], [14].
Thus, the objectives of this study were (1) to compare comorbidity data derived from self-report with administrative data in a sample of elders in the ED, (2) to determine the effect on agreement between these two data sources of sociodemographic, medical, and other factors, and (3) to compare the predictive validity of the CCI derived from the two sources.
Section snippets
Methods
This study is a secondary analysis of data from a randomized trial of a two-step intervention for older ED patients conducted in four Montreal EDs [3]. Recruitment methods have been described previously [3]. Patients aged 65 years and above, ready to be discharged home from the ED were screened using the Identification of Seniors at Risk (ISAR) screening tool [15], a short self-report screening questionnaire designed to identify patients at risk for functional decline, other adverse health
Results
Characteristics of the study population are reported in Table 1. The presence of each of the 18 comorbid conditions differed in a statistically significant way by data source (administrative vs. self-report) for nine of the conditions (data not shown). Four conditions were reported more frequently in the self-report data (myocardial infarction, ulcer disease, diabetes with end organ damage, and connective tissue disease), whereas five were reported more frequently in the administrative data
Discussion
This study examined the agreement between self-reported comorbidity conditions and administrative records in a sample of 520 older ED patients, with oversampling of frailer patients (ISAR score of 2 or more). Comparison of the CCI scores computed from administrative and self-report data indicated low levels of agreement, even in the subgroup with prior hospital admissions. There were also systematic differences in the scores, with those patients with greater prior service utilization having
Acknowledgments
Author contributions were as follows: Stephanie Susser developed the study design, carried out the literature review and the data analysis, and wrote the initial draft of the manuscript; Jane McCusker provided the data for the study, supervised the conduct of the study, and edited the manuscript; Eric Belzile assisted with the statistical analyses and with checking the data presented in the manuscript. The study sponsor had no input into the design, methods, subject recruitment, data
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