Psychometric properties of the Glaucoma Treatment Compliance Assessment Tool in a multicenter trial.

PURPOSE

To assess the psychometric properties of a new version of the Glaucoma Treatment Compliance Assessment Tool, a survey evaluating health behavior and glaucoma adherence using constructs from the Health Belief Model.

DESIGN

Psychometric analysis.

METHODS

We administered the 47-statement Glaucoma Treatment Compliance Assessment Tool to 201 participants who were using a single bottle of an ocular hypotensive agent, and objectively measured adherence with medication event monitoring system devices over 60 days. Adherence was the percentage of days with correctly timed bottle openings. We used principal components analysis to determine construct validity, Cronbach's alpha for internal consistency reliability, frequency analysis for floor and ceiling effects, and Spearman rho for test-retest reliability. We determined predictive validity using univariate and multiple regression.

RESULTS

The mean (±SD, range) adherence percentage was 79.9% (±18.5%, 20.3%-100.0%). Principal component analysis loaded 24 questions into 6 components that were consistent with the Health Belief Model. All 6 components had Cronbach's alpha reliability between 0.601 and 0.797. No statements had floor or ceiling effects, and all statements had acceptable test-retest reliability. Multiple regression analysis showed 4 Health Belief Model statements, white race, older age, and married marital status to be associated with higher adherence (adjusted R(2) = 0.27, P < .001).

CONCLUSIONS

The newest version of the Glaucoma Treatment Compliance Assessment Tool showed acceptable psychometric properties. With further refinement, clinicians and researchers could use it to examine factors related to adherence and measure improvement in adherence with a change in health behavior attitudes.