Thai Modified Dental Anxiety Scale (Thai-MDAS): cross-cultural adaptation, psychometric validation, and preliminary diagnostic accuracy

Abstract

Dental anxiety is a prevalent barrier to dental care worldwide. The Modified Dental Anxiety Scale (MDAS) is a widely used, brief self-report measure with established cross-cultural validity in numerous languages, yet no validated Thai-language version currently exists. This study aimed to cross-culturally adapt the MDAS into Thai (Thai-MDAS) and to evaluate the psychometric properties and diagnostic accuracy of the resulting Thai-MDAS. The MDAS was adapted into Thai following the five-stage cross-cultural adaptation guideline, with permission from the original developer. A cross-sectional validation study was conducted among 233 Thai adults with English proficiency. Participants completed the Thai-MDAS, a Numerical Rating Scale (NRS), and the Index of Dental Anxiety and Fear (IDAF-4 C+) in its original English form. Internal consistency was assessed using Cronbach’s alpha. Test-retest reliability was evaluated after four weeks using the intraclass correlation coefficient (ICC). Convergent validity was examined through Spearman’s correlations with the NRS and IDAF-4 C+. Known-groups validity was assessed using the Mann-Whitney U and Kruskal-Wallis tests. Receiver operating characteristic (ROC) analysis determined diagnostic accuracy and explored preliminary cut-off thresholds for this population. The Thai-MDAS demonstrated good internal consistency (α = 0.88; N = 233) and satisfactory test-retest reliability (ICC = 0.79; n = 156). Strong convergent validity was observed with the NRS ( r = 0.74) and IDAF-4 C+ core module ( r = 0.74). Known-groups analysis confirmed significantly higher scores among symptomatic dental attenders ( p = 0.02) and participants with marked dental fear ( p < 0.001), with no significant gender difference ( p = 0.85). The area under the ROC curve was 0.94. At the original cut-off of ≥ 19, sensitivity was only 42.9%. Candidate thresholds in the range of ≥ 13 to ≥ 15 demonstrated more balanced diagnostic performance. The Thai-MDAS is the first psychometrically validated Thai-language instrument for dental anxiety screening, demonstrating good reliability, strong validity, and preliminary outstanding diagnostic accuracy. Our findings suggest that the original cut-off of ≥ 19 may lead to the under-detection of anxious individuals in Thai populations, with lower thresholds showing promising diagnostic performance that warrants formal investigation. Validation in the general population, alongside prevalence exploration and cut-off optimisation, is recommended as a priority for future research.