Construct Validity of Inherited Retinal Disease–Specific Patient-Reported Outcome Measures

PURPOSE: To evaluate aspects of construct validity of the Michigan Retinal Degeneration Questionnaire (MRDQ) and the Michigan Vision-related Anxiety Questionnaire (MVAQ). METHODS: Subjects with a clinical diagnosis of an inherited retinal disease (IRD) were recruited prospectively and 3 tests were used to assess construct validity: the ability to distinguish different IRD phenotypes; test a priori hypothesis of an association between vision-related anxiety and vision-related disabilities; and correlate MRDQ and MVAQ with the National Eye Institute Visual Functioning Questionnaire 25 (NEI VFQ-25) and the Impact of Vision Impairment (IVI). One-way analysis of variance (ANOVA) was used to compare different phenotypes for mean domain scores for MRDQ/MVAQ. Pearson correlations were performed between; Cone-Function Anxiety and Central Vision controlling for better eye visual acuity, Rod-Function Anxiety and Scotopic Function controlling for visual field area (III4e and IV4e), and scores of MRDQ/MVAQ, NEI VFQ-25, and IVI. RESULTS: The study sample consisted of 146 patients evenly divided between males and females, and mean age was 50 years. The 1-way ANOVA test was significant for distinguishing IRD phenotypes in 6 domains of MRDQ/MVAQ. Cone-Function Anxiety correlated with Central Vision controlling for visual acuity, Rod-Function Anxiety correlated with Scotopic Function controlling for visual field area, and all domains in MRDQ/MVAQ had significant correlations with NEI VFQ-25 and IVI composite scores. CONCLUSION: MRDQ and MVAQ domenstrate aspects of construct-validity set forth by the US Food and Drug Administration. The study futher supports the use of both patient-reported outcome measures in IRD clinical trials and natural history studies.