Reliability and validity of the Thai version of the Yale–Brown Obsessive Compulsive Scale – Second Edition in clinical samples

PURPOSE: The Yale–Brown Obsessive Compulsive Scale (Y-BOCS) is regarded as the most acceptable tool for measuring obsessive–compulsive disorder symptom severity. Recently, the Yale–Brown Obsessive Compulsive Scale – Second Edition (Y-BOCS-II) was developed for better measurement. The study reported here aimed to evaluate the psychometric properties of the Thai version of the Yale–Brown Obsessive Compulsive Scale – Second Edition (Y-BOCS-II-T). PATIENTS AND METHODS: The original version of the Y-BOCS-II was translated into Thai, which involved forward translation, synthesis of the translation, and back translation. Modification and cross-cultural adaptation were completed accordingly. The developed Y-BOCS-II-T, together with the Hamilton Rating Scale for Depression, was administered to 41 patients who had a primary diagnosis of obsessive–compulsive disorder. The patients then completed the Pictorial Thai Quality of Life instrument and Patient Health Questionnaire. Lastly, the Global Assessment of Functioning (GAF) and the Clinical Global Impression – Severity Scale (CGI-S) of all patients were blindly rated by another experienced psychiatrist who was not the interviewer. RESULTS: The mean total score of the Yale–Brown Obsessive Compulsive Scale – Second Edition – Severity Scale (Y-BOCS-II-SS) and the Yale–Brown Obsessive Compulsive Scale – Second Edition – Symptom Checklist (Y-BOCS-II-SC) were 18.44 (standard deviation =10.51) and 15.85 (standard deviation =9.58), respectively. The Y-BOCS-II-T had satisfactory internal consistency (Cronbach’s alpha =0.94 for the Severity Scale, and Kuder–Richardson Formula 20 =0.90 for the Symptom Checklist). Inter-rater reliability was excellent for both the Y-BOCS-II-SS and Y-BOCS-II-SC. Factor analysis of Y-BOCS-II-SS items revealed a two-factor component associated with obsession and compulsion. The Y-BOCS-II-SS correlated highly with the CGI-S and GAF (r =0.75 and −0.76, respectively), but the Y-BOCS-II-SC correlated moderately (r=0.42 for CGI-S; r=−0.39 for GAF). The Y-BOCS-II-SS and Y-BOCS-II-SC slightly to moderately correlated with the Hamilton Rating Scale for Depression, Patient Health Questionnaire, and Pictorial Thai Quality of Life, which might indicate the comorbidity depression and its effect on quality of life. CONCLUSION: The Y-BOCS-II-T is a psychometrically reliable and valid measure for the assessment of both severity and characteristics of obsessive–compulsive symptoms in Thai clinical samples.