Reliability, validity, and responsiveness of the Thai version of the Dry Eye-Related Quality-of-Life Score questionnaire

Dry eye disease (DED) is a common and growing eye problem worldwide. Chronic DED symptoms can, subsequently, affect the patients' quality of life (QOL). This prospective cross-sectional study aimed to assess the reliability, validity, and responsiveness of the Thai version of the Dry Eye-Related Quality-of-Life Score (DEQS-Th) questionnaire and to evaluate its accuracy in DED screening. Psychometric validation was conducted on DED participants. All participants completed the DEQS-Th and other measurements including the Ocular Surface Disease Index (OSDI) and the 5-level EQ-5D (EQ-5D-5L). Internal consistency, concurrent validity, convergent, and discriminant validity were evaluated. The standardized response mean (SRM) was used to evaluate the responsiveness of the DEQS-Th. The optimal cut-off score of DEQS-Th for DED screening was assessed. Among 100 participants with a mean age of 50.9 ± 14.4 years, and 89.0% female, the internal consistency of the DEQS-Th was excellent (Cronbach's alpha: 0.80-0.92). The test-retest intraclass correlation was 0.82-0.92. It showed concurrent validity with the OSDI (r = 0.694, p < .001) and EQ-5D-5L index scores (r = -0.578, p < .001). DED is suspected if the DEQS-Th score ≥ 18.33 (AUC = 0.897, sensitivity 90.0%, specificity 76.7%) or its Short Form score ≥ 3 (AUC 0.857, sensitivity 93.0%, specificity 63.3%). The SRM of the symptom subscale of DEQS-Th was 0.82, indicating relatively large responsiveness, whereas the impact on daily life subscale and the summary score was small. In conclusion, the DEQS-Th is valid and reliable for evaluating the multifaceted effects of DED on a patient's QOL. It can be useful for primary assessment and monitoring of DED in routine clinical practice.