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Cataract symptom score questionnaire: Rasch revalidation.
Vijaya K Gothwal1, Thomas A Wright, Ecosse L Lamoureux
1NH&MRC Centre for Clinical Eye Research, Department of Ophthalmology, Flinders Medical Centre and Flinders University of South Australia, Bedford Park, SA 5042, Australia.
Ophthalmic Epidemiology
|October 31, 2009
Summary
The 5-item Cataract Symptom Score (CSS) has inadequate person separation, meaning it cannot effectively differentiate between cataract symptom severity. Improving the CSS may involve adding questions or using computer-adaptive testing for better measurement.
Area of Science:
- Ophthalmology
- Psychometrics
- Health Outcomes Research
Background:
- The 5-item Cataract Symptom Score (CSS) was developed to assess cataract surgery timing and outcomes.
- Classical test theory underpinned the initial development of the CSS.
- There is a need to evaluate the psychometric properties of patient-reported outcome measures.
Purpose of the Study:
- To investigate the psychometric properties of the 5-item CSS using Rasch analysis.
- To assess the reliability and validity of the CSS in a patient population awaiting cataract surgery.
Main Methods:
- Rasch analysis was performed on responses from 113 patients awaiting cataract surgery.
- Key psychometric properties examined included response category use, person separation, targeting, and unidimensionality.
- The 5-item CSS assesses bothersome symptoms such as double vision, glare, and blurry vision.
Main Results:
- Participants used the CSS response categories as intended.
- The CSS demonstrated inadequate person separation (1.74), limiting its ability to distinguish symptom severity among patients.
- The CSS was poorly targeted, with most participants not significantly bothered by the assessed symptoms.
- All items demonstrated unidimensionality, indicating the CSS measures a single construct of cataract symptoms.
Conclusions:
- The current 5-item CSS lacks sufficient discriminatory ability for individuals with cataracts.
- Enhancements could include adding more questions to the CSS.
- Developing an item bank and utilizing computer-adaptive testing may offer a superior approach for measuring cataract symptoms.
