Risk adjustment for older hospitalized persons: A comparison of two methods of data collection for the Charlson index

To compare Charlson indices based on chart data and ICD-9 data for agreemen t overall and on rating specific comorbid conditions, and to compare mortal ity risks associated with these indices. Prospective cohort study. Six gene ral medicine wards at Yale-New Haven Hospital. 524 consecutive patients who had no clinical evidence of delirium at enrollment, admitted between Novem ber 6, 1989 and July 31, 1991, aged 70 years or older. Death within 1 year of the index hospital admission date. Scores using the chart-based data wer e significantly higher than those using ICD-9 data. About half of the indiv idual conditions showed fair-to-good agreement between the two scores, wher eas the other half showed poor agreement. A comparison of mortality predict ion indicated that the weightings assigned to individual comorbidities diff ered substantially from those used in Charlson's original index. While mort ality prediction of each individual index was comparable, the ICD-9 and cha rt indices contributed independently to mortality prediction in the presenc e of the other. Low agreement between Charlson scores based on the two meth ods of data collection and their cumulative contribution to mortality predi ction suggest that these indices may include different information. Our res ults suggest that the original Charlson index may not provide optimal risk adjustment for elderly general medicine samples. We suggest development of an empirically-derived index of comorbid conditions and weights may be warr anted for older general medical patients. (C) 2001 Elsevier Science Inc. Al l rights reserved.