Predicting the EQ-5D-5L utility scores from the impact of vision impairment (IVI) questionnaire in Thai patients

Objectives : (1) This study aims to predict the EQ-5D-5L utility scores from the impact of vision impairment (IVI) questionnaire in Thai patients using mapping techniques. (2) To investigate the association between sociodemographic and clinical variables with the EQ-5D-5L index scores. Methods : This is a secondary data analysis. A total of 499 patients with multiple levels of visual impairment were recruited from King Chulalongkorn Memorial Hospital Thailand between February and July 2022. Ordinary least square (OLS), Tobit, Censored least absolute deviation (CLAD), and Adjusted limited dependent variable mixture model (ALDVMM) regression models were used to map the IVI questionnaire onto EQ-5D-5L index scores and to investigate the association between sociodemographic and clinical variables with the EQ-5D-5L index scores. IVI domain scores, IVI total score, gender, age, occupation, and best corrected visual acuity (BCVA) were included as predictors. Performance metrics including root mean square error (RMSE), mean absolute error (MAE) and adjusted R2 were used to select the best-predictive model. Results : The results indicated that EQ-5D-5L index scores were significantly associated with the reading and emotional well-being domains of the IVI. Among sociodemographic and clinical variables, only age was significantly associated with EQ-5D index scores (p < 0.01). The mean predicted EQ-5D-5L value (0.803) was lower than the mean observed value (0.808). The ALDVMM 1-component model provided the best predictive performance (RMSE 0.137, MAE 0.101, adjusted R² 0.689). Conclusions : The mapping techniques effectively predicted EQ-5D-5L utility scores from the IVI questionnaire in Thai patients. The predicted model can help the decision analysis to capture health utility and inform quality-adjusted life-years (QALYs) when vision-specific measures are available and can be further applied in health economic evaluations.