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Objective. To develop the Self-Administered Comorbidity Questionnaire (SCQ) and assess its psychometric properties, including the predictive validity of the instrument, as reflected by its association with health status and health care utilization after 1 year. Methods. A cross-sectional comparison of the SCQ with a standard, chart abstraction-based measure (Charlson Index) was conducted on 170 inpatients from medical and surgical care units. The association of the SCQ with the chart-based comorbidity instrument and health status (short form 36) was evaluated cross sectionally. The association between these measures and health status and resource utilization was assessed after 1 year. Results. The Spearman correlation coefficient for the association between the SCQ and the Charlson Index was 0.32. After restricting each measure to include only comparable items, the correlation between measures was stronger (Spearman r ‫؍‬ 0.55). The SCQ had modest associations with measures of resource utilization during the index admission, and with health status and resource utilization after 1 year. Conclusion. The SCQ has modest correlations with a widely used medical record-based comorbidity instrument, and with subsequent health status and utilization. This new measure represents an efficient method to assess comorbid conditions in clinical and health services research. It will be particularly useful in settings where medical records are unavailable.

Comorbidity generally is measured by medical record abstraction, which is expensive and often impractical. The aim of this study was to assess the reproducibility and validity of a comorbidity questionnaire. The authors developed a brief comorbidity questionnaire that included items corresponding to each element of the medical record-based Charlson index. The questionnaire was administered to 170 inpatients. Charlson scores were abstracted from these patients' medical records. We assessed test-retest reliability of the questionnaire and the Charlson index, the correlation between the questionnaire and the Charlson index, and correlations between each comorbidity measure and indicators of health resource utilization including medication use, hospitalizations in the past year, and hospital charges. Test-retest reliability, assessed with the intraclass correlation coefficient, was 0.91 for the questionnaire and 0.92 for the chart-based Charlson index. The Spearman correlation between these two measures was 0.63. The correlation between comorbidity measures was weaker in less educated patients. Correlations with indicators of resource utilization were similar for the two comorbidity instruments. The authors found that a questionnaire version of the Charlson index is reproducible, valid, and offers practical advantages over medical record-based assessments.

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