The 8-item Morisky Medication Adherence Scale: validation of a Brazilian-Portuguese version in hypertensive adults

Abstract

Background: The Morisky Medication Adherence Scale (MMAS-8) remains one of the most widely used mechanisms to assess patient adherence. Its translation and testing on languages in addition to English would be very useful in research and in practice.

Objective: To translate and examine the psychometric properties of the Portuguese version of the structured self-report eight-item Morisky Medication Adherence Scale among patients with hypertension.

Methods: The study was designed as a cross-sectional survey conducted in six Family Health Units of the Brazilian Unified Health System, in Maceió, between March 2011 and April 2012. After a standard "forward-backward" procedure to translate MMAS-8 into Portuguese, the questionnaire was applied to 937 patients with hypertension. Reliability was tested using a measure of internal consistency (Cronbach's alpha), and test-retest reliability. Validity was confirmed using known groups validity. Three levels of adherence were considered based on the following scores: 0 to <6 (low); 6 to <8 (medium); 8 (high).

Results: The mean age of respondents was 57.1 years (SD = 12.7 years), and 71.5% were female. The mean number of prescribed antihypertensives per patient was 1.62 (SD = 0.67). The mean score for the medication adherence scale was 5.78 (SD = 1.88). Moderate internal consistency was found (Cronbach's alpha = 0.682), and test-retest reliability was satisfactory (Spearman's r = 0.928; P < 0.001). A significant relationship between MMAS-8 levels of adherence and BP control (chi-square, 8.281; P = 0.016) was found. 46.0%, 33.6%, and 20.4% of patients had low, medium, and high adherence, respectively. The self-report measure sensitivity, specificity, positive and negative predictive values were 86.1%, 31.2%, 57.4% and 68.3% respectively.

Conclusions: Psychometric evaluation of the Portuguese version of the MMAS-8 indicates that it is a reliable and valid measure to detect patients at risk of non-adherence. The MMAS-8 could still be used in routine care to support communication about the medication-taking behavior in hypertensive patients.

Keywords: Cross-cultural adaptation; Hypertension; Medication adherence; Morisky scale; Self-reported adherence; Validation.