Psychometric properties of the Thai version of the orthognathic quality of life questionnaire (OQLQ-Th)

Background: Dentofacial deformities significantly impact patients’ quality of life, yet validated instruments for assessing oral health-related quality of life in Thai populations are limited. This study aimed to develop a Thai version of the Orthognathic Quality of Life Questionnaire (OQLQ-Th) through cross-cultural translation and to evaluate its psychometric properties. Methods: The OQLQ was translated into Thai using a forward-backwards translation methodology. Psychometric evaluation was conducted with 193 patients with dentofacial deformities at Mahidol University. Reliability was assessed through internal consistency and test-retest analyses. Validity was determined through content, construct, discriminant, and convergent validity testing. Results: Content validity assessment yielded a Scale-Content Validity Index (S-CVI) of 0.86. The questionnaire demonstrated excellent internal consistency (Cronbach’s alpha = 0.931) and test-retest reliability (Spearman correlation = 0.913). Exploratory factor analysis identified four distinct domains. Discriminant validity showed significant differences across severity levels and treatment needs (p < 0.05). Convergent validity was confirmed with a Spearman correlation of 0.679. Conclusions: The OQLQ-Th demonstrates robust reliability and validity for assessing quality of life in Thai patients with dentofacial deformities. The proposed 16-item OQLQ-Th creates a shorter version that reduces patient burden while maintaining measurement precision. This validated instrument provides clinicians and researchers with a reliable tool for evaluating oral health-related quality of life in Thai-speaking populations.