Evaluation of the Chinese Adult Strabismus-20 (CAS-20) questionnaire using Rasch analysis
Meiping Xu, Jingwei Zheng, Xinping Yu, Yuanyuan Chen, Huanyun Yu
Published 2015-04-25
Cite as Chin J Optom Ophthalmol Vis Sci, 2015, 17(4): 221-227. DOI: 10.3760/cma.j.issn.1674-845X.2015.04.008
Abstract
ObjectiveTo further refine the Chinese Adult Strabismus-20 (CAS-20) healthrelated quality of life (HRQOL) questionnaire using Rasch analysis.
MethodsIn this crosssectional study, the CAS- 20 questionnaire was independently completed by 246 adult strabismus patients. Based on the score for each item, Rasch analysis was performed on the original CAS-20 using the following aspects: dimensionality, response order, local dependence, infit and outfit analysis, differential item function, subject targeting and confirmatory dimensionality.
ResultsThe original CAS-20 was divided into 4 subscales, which were labeled ″self-perception″, ″interaction″, ″reading function″, and ″general function″. Response ordering was appropriate for all of the 4 subscales. As a result of infit and outfit analysis, 3 items were removed, one each from "selfperception″, ″reading function″, and ″general function″. No significant differential item function was found for sex or age. Compared with the ability of the patients and item difficulty, the 3 subscales matched well except for ″reading function″.
ConclusionThe original CAS-20 was reduced to 17 items, and divided into 4 subscales, which were ″self-perception″, ″interaction″, ″reading function″, and ″general function″. Subject response choices saved 5 test options. The refined CAS- 20 may prove to be more responsive to HRQOL changes in adult strabismus patients.
Key words:
Rasch analysis; Adult strabismus health related quality of life questionnaire; Subscale; Strabismus
Contributor Information
Meiping Xu
Eye Hospital of Wenzhou Medical University, Wenzhou 325027, China
Jingwei Zheng
Xinping Yu
Yuanyuan Chen
Huanyun Yu