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Psychometric Properties of the Glaucoma Treatment Compliance Assessment Tool (GTCAT) in a Brazilian Population

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To determine the psychometric properties of a reduced version of the Glaucoma Treatment Compliance Assessment Tool (GTCAT), which was translated to Brazilian Portuguese.

Patients and Methods:

We translated into Portuguese the GTCAT using validated techniques and administered it to a group of glaucoma patients using at least 1 ocular hypotensive eye drop medication. We used principal components analysis to determine construct validity, Rasch analysis, and Cronbach α for internal consistency reliability, frequency analysis for floor and ceiling effects, and Spearman ρ for test-retest reliability.


We included 76 glaucoma patients. Principal component analysis loaded 14 questions into 7 components that were consistent with the Health Belief Model. The components were related to “barriers due to lack of drops,” “self-efficacy,” “experience of negative effects of the disease,” “well-being,” “general glaucoma knowledge,” “glaucoma symptoms,” and “cues-to-action.” No statements had floor or ceiling effects, and all statements had acceptable test-retest reliability. Components had internal consistency Cronbach α reliability between 0.125 and 0.794. and average Spearman ρ reliability was 0.73, ranging from 0.44 to 1.00. According to Rasch analysis, the mean (±SD) of the person measures was 0.24±0.15 logits, person separation index was 0.58, and person reliability 0.25.


The Portuguese-translated version of the GTCAT showed acceptable psychometric properties. With further refinement, clinicians and researchers could use it to better investigate glaucoma adherence issues in the Brazilian population.
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Keywords: adherence; compliance; glaucoma; medication; treatment

Document Type: Research Article

Affiliations: 1: Hospital Oftalmológico de Brasília, Brasília, Distrito Federal, Brazil 2: Devers Eye Institute at Legacy Health, Portland, OR

Publication date: March 1, 2018

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