The Brief Medication Questionnaire and Morisky-Green test to evaluate medication adherence

To analyze the reliability and performance of the Portuguese version of questionnaires used to evaluate adherence to hypertensive treatment.

Hypertensive patients attending a primary healthcare unit in Porto Alegre, Southern Brazil, from January to September 2010, were randomly selected (n = 206). To evaluate adherence, Portuguese versions of the Morisky-Green test (MGT) and the Brief Medication Questionnaire (BMQ) were used. The analysis considered internal consistency, temporal stability and performance compared to three gold standards, which are: inadequate control of blood pressure (BP > 140/90 mmHg); insufficient rate of medication acquisition at the institution's pharmacy (<80%) and a combination of both factors.

Of the patients studied, 97 only used medications dispensed by the Basic Health Unit. The tests showed good internal consistency by Cronbach's α: BMQ 0.66 (95%CI 0.60 to 0.73) and the MGT 0.73 (95%CI 0.67 to 0.79). The BMQ Regimen Screen had a sensitivity of 77%, specificity of 58%, and an area under the ROC curve of 0.70 (95%CI 0.55 to 0.86); for MGT sensitivity was 61%, specificity 36% and area under the ROC curve 0.46 (95%CI 0.30 to 0.62). The correlation between the BMQ and the MGT was r=0.28, p> 0.001. Low adherence per the BMQ is associated with higher blood pressure levels when compared to adherent patients (148.4 [SD 20.1] vs 128.8 [SD 17.8]; p <0.001), but not for the MGT.

The BMQ showed better performance than the MGT, with greater sensitivity and specificity. Evaluation of adherence may help clinicians discriminate between inadequate use of medication and insufficient treatment regimen.