Development and validation of comorbidity index in South Korea

Abstract

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.