Development and validation of comorbidity index in South Korea.

OBJECTIVE This study aims to develop and validate a new comorbidity index using data from hospitalized patients in South Korea. STUDY DESIGN Retrospective cohort study. SETTING Hospital inpatients. STUDY PARTICIPANTS Data from 4677 hospitalized patients aged 40-79 who had admitted in a medical center in Korea between September and December in 1997 were individually linked to national mortality data through December 2007. Among them, 3274 patients (70%) were randomly included in the development data set and the other 1403 patients (30%) in the validation data set. Another 3413 liver cancer patients from the same hospital were used to validate the index. MAIN MEASURE Comorbidity index and mortality risk. RESULTS Based on mortality using stratified Cox regression analyses, comorbidity scores ranging from 1 to 4 were assigned for 20 comorbid conditions. Summation of the scores produced the new comorbidity index (Asan comorbidity index, ACI). C-indices in the Cox regression analyses showed the greatest increase [0.589 (95% confidence interval, 0.568-0.609) in age- and sex-adjusted model; 0.697 (0.678-0.716) in the ACI and 0.664 (0.645-0.684) in the Charlson comorbidity index, respectively] when the ACI was added in the validation models. CONCLUSIONS A newly developed comorbidity index using Korean hospitalized patient data based on the International Classification of Disease, 10th Revision (ICD-10) was valid among both general medical inpatients and liver cancer patients. This index may well be widely used in various health-care settings in Korea where patients' information on health conditions is coded with ICD-10.