Translation and validation of the Chinese version of the general medication adherence scale (GMAS) in patients with chronic illness

Abstract

Objective To translate the English version of general medication adherence scale (GMAS) into a Chinese version and test its reliability and validity in Chinese patients with chronic diseases. Methods After translating the original English version into Chinese (GMAS-C) following the forward-backward translation and expert review procedure, we conducted a pilot study among 10 chronic disease patients. Each patient took about 10 min to complete the scale and was asked about the difficulty of understanding or filling the scale. Then a total of 312 patients aged 18 years or older with chronic illness were selected from the outpatient departments of two tertiary hospitals and a community center in Tianjin from April 2019 to May 2020 by convenience sampling. Cronbach’s α coefficient, item-total correlation and test–retest reliability were used to evaluate the scale reliability; expert evaluation method was used to evaluate the content validity of the scale; and exploratory factor analysis, confirmatory factor analysis, and known group validity were used to evaluate the construct validity of the scale. Results As a result of the adaptation process, the GMAS-C’s structure was determined. It included 3 dimensions and 11 items and was reliable and valid for Chinese patients with chronic diseases. Total Cronbach’s α coefficient of the scale was 0.781 and test–retest reliability coefficient was 0.883 after two weeks. The item-level content validity indexes (CVIs) were ≥ 0.78 for all items. A Kaiser–Meyer–Olkin test and Bartlett’ test of sphericity test indicated that the sample met the requirements of factor analysis. Exploratory factor analysis extracted three factors with eigenvalue >1, and 60% of the total variance was explained by three-factor solution. Confirmatory factor analysis showed acceptable fit indices (χ 2/df = 1.58, IFI = 0.96, TLI = 0.94, CFI = 0.96 and RMSEA = 0.05). Conclusions The GMAS-C demonstrates satisfactory reliability and validity. This scale can be a clinically useful tool to identify the levels of medication adherence and possible barriers for adherence of the medication regime in patients with chronic diseases.