Abstract
Purpose: :
We created the Glaucoma Treatment Compliance Assessment Tool (GTCAT) to determine the factors related to compliance with ocular hypotensive medications. We were interested in the construct validity and reproducibility.
Methods: :
We enrolled 60 consecutive glaucoma patients from a tertiary practice into this cross-sectional survey. We determined construct validity using Principal Components Analysis (PCA), internal consistency reliability, and frequency analysis of floor and ceiling effects. We used paired t-tests, Pearson’s correlations, chi-square, McNemar’s test, and Intraclass Correlation Coefficients, as applicable, to determine reproducibility.
Results: :
PCA showed significant factor loadings on 8 components and 7 were consistent with the constructs of the Health Belief Model (severity, benefits, self-efficacy, barriers, knowledge, susceptibility, and cues-to-action). Of these 7 components, 4 (Severity, Benefits, Self-Efficacy and Barriers) showed acceptable internal consistency reliability (Cronbach’s α > 0.70); knowledge showed borderline reliability (α=0.64); and susceptibility had poor reliability (α = 0.38). We could not determine internal consistency for cues-to-action since it only included 1 question. We excluded 2 (8 %) out of 25 questions from the reproducibility analysis because of ceiling effects. Reproducibility was 91% (21/23). Intraclass Correlation Coefficients were excellent (r≥0.60) for 15 (75%) questions and acceptable (r≥0.40) for 18 (90%) out of 20 questions.
Conclusions: :
These preliminary data suggest that the GTCAT has good construct validity and reproducibility. Removing questions with poor reliability or ceiling effects will result in a shorter questionnaire. We need to evaluate content validity and predictive validity prior to clinical implementation.
Keywords: clinical (human) or epidemiologic studies: biostatistics/epidemiology methodology • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials