Development of Korean Frailty Index for Primary Care (KFI-PC) and Its Criterion Validity

Background: The objective of this study was to develop and validate the Korean Frailty Index for Primary Care (KFI-PC) based on a comprehensive geriatric assessment. Methods: We developed a 54-item KFI-PC comprising 10 standard domains: cognitive status including delirium or dementia; mood; communication including vision, hearing, and speech; mobility; balance; bowel function; bladder function; ability to carry out activities of daily living; nutrition; and social resources. To test its validity, we applied KFI-PC to participants of the Korean Frailty Aging and Cohort Study (KFACS). We analyzed 1,242 participants (mean age, 77.9 +/- 3.9 years; 47.2% men) from the KFACS who visited 10 study centers in 2018, after excluding 32 participants with missing data required to assess Fried's physical frailty phenotype. Results: The mean KFI-PC score was 0.17 +/- 0.08, ranging from 0.02 to 0.52. The median KFI-PC score was higher in women than in men, and there was a trend toward higher values in older age groups. The prevalence of frailty when applying a generally used frailty index cutoff point of >0.25 was 17.5% in the whole study sample. As a construct validation of KFI-PC, the area under the receiver operating characteristic curve for Fried's physical frailty was 0.921, and the optimal cutoff value to predict frailty phenotype was 0.23. The KFI-PC score also correlated well with physical, cognitive, and psychological functions; nutritional status; disability in activities of daily living; and instrumental activities of daily living. The Cronbach's alpha coefficient of the 54 total items was 0.737. Conclusion: We developed KFI-PC with 53 deficits, including comprehensive geriatric assessment components, and demonstrated the acceptable construct validity and internal consistency of KFI-PC.