Can Comorbidity Be Measured By Questionnaire Rather than... : Medical Care (original) (raw)

Original Article

KATZ, JEFFREY*; CHANG, LILY†,‡; SANGHA, OLIVER†; FOSSEL, ANNE†; BATES, DAVID§

*From the Department of Rheumatology and Immunology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.

†From the Robert Brigham Multipurpose Arthritis and Musculoskeletal Disease Center, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.

‡From the School of Medicine, Tufts University, Boston, Massachusetts.

§From the Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.

Supported in part by grant AR36308 from the National Institutes of Health. Dr. Katz is supported in part by an Arthritis Investigator Award from the Arthritis Foundation. Ms. Chang was supported by a Summer Medical Student Research Fellowship from the American College of Rheumatology. Dr. Sangha was supported by a research fellowship from the German Academic Exchange Service. Dr. Bates was supported in part by National Research Service Award 1F32 HS00040-01 from the Agency for Health Care Policy Research.

Presented in part at the 1994 Annual Meeting of the Society of General Internal Medicine, Washington, DC.

Address correspondence to: Jeffrey N. Katz, Department of Rheumatology and Immunology, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115.

Abstract

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.