Catquest-9SF questionnaire: validation of the Portuguese version using the Rasch analysis

ABSTRACT Purpose: The aim of this study was to validate the Portuguese version of Catquest-9SF through its application in a native Brazilian population with cataracts and to determine the correlation of the questionnaire scores with preoperative visual acuity. Methods: A prospective study was conducted to validate the Catquest-9SF questionnaire, which was translated and back-translated, generating a final version in Portuguese. A total of 120 Brazilian patients awaiting cataract surgery were recruited to answer the questionnaire and to document their preoperative data and visual acuity. The Rasch analysis was used to assess the instrument’s psychometric properties. Results: The Portuguese version of Catquest-9SF demonstrated an acceptable adjustment of the items (item fit statistics ranging from 0.7 to 1.3), unidimensionality (principal component analysis), and good organization in the item response categories (thresholds of the categories: -2.79, 0.57, and 2.22, respectively). The questionnaire contains items with stable relationships if considered at the same level of visual impairment in the comparison between the two groups (absence of differential item functioning). The separation of people (person separation index, 3.07) was adequate. The visual acuity in the logarithm of the minimum angle of resolution (logMAR) in the best eye with the best optical correction showed a statistically significant correlation with the Catquest-9SF logit score (r=0.282 and p=0.004). Conclusions: The Portuguese version of Catquest-9SF presents evidence of validity and reliability, in addition to being linguistically and culturally understandable for Portuguese-speaking patients born in Brazil. The questionnaire is easy to understand and quick to apply, as it could adequately estimate the subjective visual functioning in patients with cataracts. We found a significant correlation between visual acuity and the questionnaire score.

摘要

研究目的：本研究旨在针对巴西本土白内障患者群体应用Catquest-9SF问卷，并对其葡萄牙语版本进行效度验证，同时探究该问卷得分与术前视力的相关性。

研究方法：本研究为前瞻性验证研究，用于评估Catquest-9SF问卷的效度。研究团队首先对该问卷进行翻译与回译，最终形成葡萄牙语定稿版本。共招募120名等待白内障手术的巴西患者，要求其填写问卷，并记录其术前相关数据与视力情况。采用拉施分析（Rasch analysis）评估该量表的心理测量学特性。

研究结果：Catquest-9SF问卷的葡萄牙语版本展现出良好的条目拟合度（条目拟合统计量取值范围为0.7至1.3）、单维性（经主成分分析验证），且条目反应类别组织良好（类别阈值分别为-2.79、0.57与2.22）。在视觉损伤程度相当的两组患者对比中，问卷各条目关系稳定，未出现项目功能差异（differential item functioning）。个体分离指数（person separation index）为3.07，符合分析要求。经最佳光学矫正后的最优眼的最小分辨角对数（logarithm of the minimum angle of resolution，logMAR）视力与Catquest-9SF问卷的logit得分呈显著统计学相关（r=0.282，p=0.004）。

研究结论：Catquest-9SF问卷的葡萄牙语版本具备良好的效度与信度，且针对巴西籍葡萄牙语患者具备语言与文化适配性。该问卷易于理解、填写便捷，可有效评估白内障患者的主观视觉功能。本研究证实视力与问卷得分之间存在显著相关性。