Self-reported adherence by MARS-CZ reflects LDL cholesterol goal achievement among statin users: validation study in the Czech Republic

Rationale, aims and objectivesMeasuring self-reported adherence may contribute to minimizing the risk of therapy failure. Hence, the main aim of the study was to assess the psychometric properties of the Czech version of Medication Adherence Report Scale (MARS-CZ) and its appropriateness for use in long-term statin therapy where goal levels of low-density lipoprotein cholesterol (LDL-c) should be achieved. MethodsAnonymous structured interview was performed to determine self-reported adherence by MARS-CZ in outpatients chronically treated with statins. At the same time, medication records were reviewed for inclusion of patients into groups of those who achieved and do not achieved LDL-c goal according to cardiovascular risk level. Reliability and validity of MARS-CZ were tested as well as the relationship between adherence and LDL-c goal achievement was examined. ResultsA total of 136 (86.6%) patients completed the interview; mean age was 66.1years; 49.3% were male. The mean score of MARS-CZ was 24.4 and showed positive skewing. Satisfactory internal consistency (Cronbach's =0.54), strong test-retest reliability (r=0.83, P<0.001; intra-class correlation=0.63, 95% confidence interval: 0.35-0.81) and positive correlation with eight-item Morisky Medication Adherence Scale (r=0.62, P<0.001) were indicated. Low validity values were found between MARS-CZ and 12-item Short Form Health Survey mental and physical subscales. MARS-CZ score significantly correlated with LDL-c goal achievement (P<0.05) when all patients who achieved LDL-c goal (35%) reported high adherence to statin. MARS-CZ score also correlated with cardiovascular risk level and doctor's judgments on adjusting treatment targets for each patient. ConclusionThis study proved MARS-CZ as an acceptable self-reported adherence measure. In routine clinical practice, MARS-CZ could be helpful to reveal medication non-adherence before the alteration of drug regimen and thereby contributing to enhancement of statin therapy management.