Validation of the Korean Quick Dementia Rating System (K-QDRS).

Background The Quick Dementia Rating System (QDRS) is a brief and rapid dementia staging tool that does not require a trained rater. Objective The purpose of this study is to demonstrate the validity, reliability, and diagnostic usefulness of the Korean version of the QDRS (K-QDRS). Methods We collected a total of 411 subject-informant dyads including cognitively unimpaired (CU, n = 22), mild cognitive impairment (MCI, n = 198), and dementia (n = 191). The Clinical Dementia Rating (CDR) scale, Korean version of the Mini-Mental State Examination (K-MMSE), Korean version of instrumental activity of daily living (K-IADL), Short Form of the Geriatric Depression Scale, Caregiver-Administered Neuropsychiatric Inventory (CGA-NPI), and detailed neuropsychological tests were administered as gold standards of dementia staging, cognition, function, mood, and behavior. Results Internal consistency of the K-QDRS was excellent with Cronbach's alpha of 0.933. Concurrent validity was also satisfactory, with the K-QDRS correlating highly with the CDR Sum of Boxes (Pearson's r = 0.791), K-MMSE (Pearson's r = -0.518), K-IADL (Pearson's r = 0.727), and CGA-NPI (Pearson's r = 0.700). The K-QDRS was highly correlated with the global CDR, K-IADL, and CGA-NPI. We suggested two types of comparisons (for initial diagnosis and for follow-up evaluation). The cutoff scores for follow-up were 1.0 for MCI, 3.5 for very mild dementia, 6.5 for mild dementia, and 11.0 for moderate dementia. Conclusion The K-QDRS is a valid and reliable dementia rating questionnaire and can be used, briefly and rapidly, in various settings like clinical practices, longitudinal cohort studies, and community primary care.