Discriminative capacity of the 6-item Vision-related Quality of life and Limitations questionnaire (VQL-6)

Purpose The 6-item Vision-related Quality of life and Limitations questionnaire (VQL-6) is a screening instrument that signals a need for additional low vision care in patients with chronic ophthalmic diseases. This study aims to (1) determine the optimal scoring method for the VQL-6 and (2) evaluate its discriminative capacity for clinical use. Methods Patients with glaucoma and retina- and cornea-related disorders completed the VQL-6 and participated in an interview designed to distinguish between patients with and without a need of additional care. For the two subscales (general health and quality of life, HQOL, and vision-related limitations, VL) we compared a scoring model with equal item weights to a cross-validated model using regression weights. The optimal scoring method and discriminative capacity of the subscales were determined using receiver operating characteristics (ROC) analysis, with the interview outcome as gold standard. Sensitivities were evaluated at specificities of 90 and 95%. Results In 297 interview assessments, 96 patients (32%) appeared to need additional care. Both scoring models demonstrated very similar area under the ROC curves (AUC). The selected equal weight model yielded an AUC of 0.91 (95% confidence interval 0.87-0.94) for VL and 0.71 (0.65-0.77) for HQOL. For VL, sensitivity was 72 and 64% at 90 and 95% specificity, respectively. Corresponding HQOL sensitivities were 34 and 17%. Conclusions The subscale VL shows excellent discriminative capacity and outperformed HQOL. Future studies should explore the feasibility of the VQL-6 in clinical practice.