Psychometric properties of the Vietnamese Catquest-9 Short Form questionnaire

© Lippincott Williams & Wilkins. SIGNIFICANCE The Catquest-9 Short Form (SF) has good psychometric properties but was not available in Vietnamese. This study provides the Vietnamese Catquest-9SF and evidence supporting for its use in hospital settings along with clinical assessment to evaluate visual function. PURPOSE The purpose of this study was to evaluate the psychometric properties of the Vietnamese Catquest-9SF. METHODS Literate patients with unilateral/bilateral cataract, without severe systemic and ocular comorbidities, aged 50+ years, and scheduled for first-eye surgery were screened and recruited at the University of Medicine and Pharmacy at Ho Chi Minh City and Trung Vuong Hospital. Age, sex, and education were self-reported. The Catquest-9SF and the 25-item National Eye Institute Visual Function Questionnaire were used to assess vision-related quality of life (VRQOL). Best-corrected unilateral and bilateral log of the minimum angle of resolution (logMAR) visual acuity was measured, as was best-corrected Pelli-Robson contrast sensitivity. Rasch analysis was performed on the Vietnamese version of the Catquest-9SF. Criterion validity and convergent validity were also evaluated. RESULTS Andrich thresholds and response categories on each Catquest-9SF item were ordered, indicating that patients were able to discriminate VRQOL levels. Person separation index and reliability were 2.51 and 0.86, respectively, indicating that the Catquest-9SF was able to distinguish between patients with low- and high-vision difficulties. The tool was unidimensional, with all items fitting well within the construct. There was no evidence of differential item functioning by sex, age group, or cataract status. The tool also showed criterion validity, correlating significantly with visual acuity in the better eye (r = -0.46), the worse eye (r = -0.39), and both eyes (r = -0.44), and with contrast sensitivity for the better eye (r = 0.41), the worse eye (r = 0.32), and both eyes (r = 0.39). A strong correlation between the Catquest-9SF and the 25-item National Eye Institute Visual Function Questionnaire (r = 0.87) indicated convergent validity. CONCLUSIONS The Vietnamese Catquest-9SF is valid and psychometrically robust for assessing VRQOL among cataract patients.