Validation of the Filipino Catquest-9SF Questionnaire for Cataract Patients

Objective: The objective of this study was to determine the validity and reliability of a Filipino translation of the Catquest 9-SF questionnaire for measuring the patient reported visual outcomes of Filipino cataract patients in a tertiary hospital. Methods: The English version of the Catquest-9SF questionnaire was translated into Tagalog or Filipino, back translated into English and finally translated again into Filipino using the WHO forward backward-forward translation technique. The final Filipino version of the questionnaire was administered to 90 patients who were awaiting cataract surgery and fit the inclusion criteria. The response patterns as well as the overall construct of the Filipino questionnaire were evaluated using the Rasch model in terms of specific components for reliability and validity. Results: The Filipino version of the Catquest-9SF showed high reliability for person and item components based on Person Separation Index (PSI). All questions showed good fit statistics based on Show Mean Square (MNSQ), as well as unidimensionality using Principal Component Analysis (PCA). Differential Item Functioning (DIF) was not seen across all age groups, while only one question showed DIF among different sex groups. Conclusion: The results of the Rasch analysis show good overall functioning of the Filipino version of the Catquest-9SF. It is a valid and reliable tool that can be used to measure the visual disability outcomes of Filipino cataract patients.