Adaptation and validation of a modified version of the patient health questionnaire (PHQ-9) for a Tamil speaking population in Sri Lanka: a cross-sectional study

The patient health questionnaire (PHQ-9) is a widely used self-administered depression screening tool. Multiple Tamil translations of the PHQ-9 have been developed for different Tamil-speaking populations. This study evaluated the existing Tamil translations for their accuracy, and culturally adapted and validated the most suitable version for use among Sri Lankan Tamil speakers. Tamil translations developed for India, Singapore and Sri Lanka were evaluated for translation accuracy and cultural relevance. The Indian Tamil version which was the most accurate version was modified and culturally adapted for use in Sri Lanka and assessed in three districts where three different Tamil dialects are spoken in Sri Lanka. 898 participants responded to the survey. The culturally adapted questionnaire demonstrated good internal consistency reliability (Cronbach’s alpha = 0.833) and test-retest reliability (ICC = 0.88). Exploratory factor analysis supported a one-factor structure explaining 55% of the variance. Confirmatory factor analysis supported a unidimensional model only after allowing correlated residuals between selected items. Only configural invariance was achieved across dialect groups. The results indicated that the modified version of the Tamil PHQ-9 questionnaire has satisfactory psychometric properties and can be used to assess depressive symptoms among Tamil speakers across different dialect groups in Sri Lanka.