Validation and psychometric evaluation of the Diabetes Quality-of-Life Brief Clinical Inventory: Tamil version (DQoL-BCI-T)

Diabetes mellitus (DM) significantly impairs quality of life (QoL) through its chronic course, treatment burden, and complications. Disease-specific QoL tools provide more clinically relevant assessment than generic instruments. Although the Diabetes Quality of Life–Brief Clinical Inventory (DQOL-BCI) has been widely validated internationally, no validated Tamil version exists despite large Tamil-speaking populations affected by type 2 diabetes mellitus (T2DM). This study aimed to translate, culturally adapt, and validate a Tamil version of the DQOL-BCI (DQOL-BCI-T) among Tamil-speaking adults with T2DM in Sri Lanka. A cross-sectional validation study of DQOL-BCI-T was conducted among 165 native Tamil-speaking adults with T2DM attending an urban outpatient clinic in Colombo from May to October 2025). Translation followed a standardized forward–backward procedure with expert panel review and cognitive debriefing. Reliability was assessed using Cronbach’s alpha. Construct validity was evaluated through convergent validity with the Tamil WHOQOL-BREF and discriminant validity across clinical variables. Factor structure was examined using principal component analysis with oblimin rotation. The DQOL-BCI-T demonstrated acceptable internal consistency (Cronbach’s α = 0.682) and stability over two weeks. Significant moderate negative correlations with WHOQOL-BREF total ( r = − 0.559, p < 0.001) and domain scores supported convergent validity. Discriminant validity was demonstrated by significantly lower QoL among patients with microvascular complications ( p = 0.040). Factor analysis showed satisfactory sampling adequacy (KMO = 0.729) and acceptable item loadings, explaining 72% of total variance. The DQOL-BCI-T demonstrates satisfactory validity, reliability, and cultural appropriateness for measuring diabetes-specific quality of life among Tamil-speaking adults with T2DM. Its concise format and strong psychometric performance make it a practical tool for routine clinical assessment and research, supporting patient-centred diabetes care. Further validation across diverse clinical populations, socio-cultural contexts, and treatment regimens is warranted to confirm its broader applicability and generalisability.