Psychometric assessment of the chinese version of the indian vision functioning questionnaire based on the method of successive dichotomizations

Abstract

Purpose: The purpose of this study was to assess whether a Chinese translated version of the 33-item Indian Vision Function Questionnaire (IND-VFQ-33) forms a valid measurement scale and to evaluate its psychometric properties based on the method of successive dichotomizations (MSD). Methods: The English version of the IND-VFQ-33 was translated, back translated, and cross-culturally adapted for use in China. It was interviewer administered to patients with cataracts. MSD, a polytomous Rasch model that estimates ordered thresholds, was used to assess and optimize psychometric properties of the overall scale and three subscales separately. Results: One hundred and seventy-nine patients provided complete responses. After the removal of 2 misfitting items, a revised 31-item overall scale demonstrated adequate precision (person reliability [PR] = 0.92) and no misfitting items. The general functioning subscale fit the MSD model well after removing two misfitting items. The psychoso-cial impact subscale and the visual symptoms subscale were not considered further due to poor measurement precision. After addressing psychometric deficiencies, a 31-item overall scale (IND-VFQ-31-CN) and a 19-item general functioning subscale (IND-VFQ-GF-19-CN) were developed. Conclusions: The original IND-VFQ-33 required re-engineering to form valid measures for use in China. The revised overall scale and general functioning subscale demonstrated adequate MSD based psychometric properties. Translational Relevance: The revised IND-VFQ-33 is a valid patient-reported outcome assessment for Chinese patients with cataract based on MSD analysis.