Validation of the K6/K10 Scales of Psychological Distress and Their Optimal Cutoff Scores for Older Koreans

This study aims to assess the psychometric properties of the Korean versions of the Kessler 6 and 10 (K-K6/K10) to validate the two scales in relation to the Korean versions of the Geriatric Depression Scale-Short Form (K-GDS-SF) and the Center for Epidemiological Studies Depression Scale (K-CES-D) and to propose optimal cutoff scores appropriate for the elderly Korean population (n = 331). Psychometric performance was assessed with sensitivity, specificity, receiver operating characteristic curves, and area under the receiver operating characteristic curve. Cutoff scores were estimated from the Youden index, the closest-to-(0,1), and the balanced score. This study found that the K-K6 and K-K10 appeared to be robust screening tools, with the K-CES-D and K-GDS-SF as reference measures. The cutoff scores for the Korean senior population are proposed to be 12/13 for the K-K6 and 20/21 for the K-K10. This study indicates that the K6 and K10 can be valid and reliable screening tools of psychological distress for Korean seniors and may also be used among the Korean American elderly in the United States for both clinical and research purposes.