Interpretation of change scores for the National Eye Institute Visual Function Questionnaire-25: the minimally important difference. Issue 11 (18th May 2021)

• Record Type: Journal Article
• Authors: Burr, Jennifer M; Cooper, David; Ramsay, Craig R; Che Hamzah, Jemaima; Azuara-Blanco, Augusto
• Is Part Of: British journal of ophthalmology. Volume 106:Issue 11(2022)
• Page Start: 1514
• Page End: 1519
• Publication Date: 2021-05-18
• Subjects: glaucoma -- epidemiology; Ophthalmology -- Periodicals; 617.7
• DOI: 10.1136/bjophthalmol-2021-318901
• Languages: English
• ISSNs: 0007-1161

Abstract

Abstract : Aim: To estimate the minimally important difference (MID) in change in National Eye Institute Visual Function Questionnaire-25 (VFQ-25) composite score using methods aligned with patient perception. Methods: Retrospective analysis of prospectively collected data from adults with primary angle closure or primary angle closure glaucoma enrolled in the Effectiveness, in Angle-closure Glaucoma, of Lens Extraction study. We included data from 335 participants with patient reported visual function (VFQ-25) and health status measured by the EQ-5D-3L over 36 months. We used the recommended anchor-based methods (receiver operating characteristic (ROC), predictive modelling and mean change) to determine the MID of the VFQ-25. EQ-5D-3L anchor change was defined as none (<0.065); minimal (0.065≤EQ-5D-3L change ≤0.075 points) and greater change (>0.075 points). Results: Mean baseline VFQ-25 score was 87.6 (SD 11.8). Estimated MIDs in the change in VFQ-25 scores (95% CI) were 10.5 (1.9 to 19.2); 3.9 (−2.3 to 10.1); 5.8 (1.9 to 7.2) and 8.1 (1.7 to 14.8) for the 'within-patient', 'between-patient' change, ROC and predictive modelling anchor methods respectively. Excluding estimates from the methodologically weaker 'within-patient' method, the MID of a change in VFQ-25 composite score is 5.8 (median value). Conclusions: Estimates of the MID using multiple methods assist in the interpretation of the VFQ scores. In the context of early glaucoma related visual disability, a change score of around six points on the VFQ-25 is likely to be important to patients. Further confirmatory research is required. Studies comparing changes in patient-reported outcome measure scores with a global measure of patients' perceived change are required.