Published in:
01-10-2020 | Cornea
Both sub-scales of the “Keratoconus End-Points Assessment Questionnaire” (KEPAQ) are unidimensional and reliable
Published in: Graefe's Archive for Clinical and Experimental Ophthalmology | Issue 10/2020
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Background
Measuring quality of life in keratoconus is important and demands for well-constructed instruments and scales. To date, the Keratoconus End-Points Assessment Questionnaire (KEPAQ) is the only disease-specific scale to measure both functional and emotional compromise due to disease. Nevertheless, not much information exists regarding whether both sub-scales of the test show unidimensionality, a necessary condition in well-functioning instruments.
Methods
A sample of patients with a confirmed diagnosis of keratoconus were administered the full version of the KEPAQ. A Rasch analysis and principal component analysis were performed.
Results
A total of 249 patients with keratoconus were included. Their average age was 29.19 ± 10.91 years, and 51.40% were male. Mean score for the KEPAQ-E was 2.51 ± 3.29 logit while it was 2.26 ± 3.70 logit for the KEPAQ-F. For both sub-scales, Kaiser Criterion, Scree Plot Criterion, and Variability Criterion demonstrated unidimensionality. Reliability as measured by Cronbach’s alpha was 0.85 for the KEPAQ-E and 0.87 for the KEPAQ-F.
Conclusions
The KEPAQ is a robust, well-designed disease-specific questionnaire that shows unidimensionality. It can be reliably used to measure quality of life in keratoconus patients.