A systematic review finds inconsistency in the measures used to estimate adherence and persistence to multiple cardiometabolic medications

OBJECTIVES: We reviewed measures used to estimate adherence and persistence to multiple cardiometabolic medications from prescription data, particularly for blood pressure-lowering, lipid-lowering, and/or glucose-lowering medication, and give guidance on which measures to choose. STUDY DESIGN AND SETTING: A literature search of Medline, Embase, and PsycINFO databases was conducted to identify studies assessing medication adherence and/or persistence for patients using multiple cardiometabolic medications. Two reviewers performed the study selection process independently. RESULTS: From the 54 studies assessing adherence, only 36 (67%) clearly described the measures used. Five measures for adherence were identified, including adherence to "all," to "any," to "both" medication, "average adherence," and "highest/lowest adherence". From the 22 studies assessing persistence, only six (27%) clearly described the measures used. Three measures for persistence were identified, including persistence with "all," with "both," and with "any" medication. Less than half of the studies explicitly considered medication switches when relevant. CONCLUSION: From the identified measures, the "any medication" measure is most suitable for identifying patients in need of an intervention, whereas the "all medication" measure is useful for assessing the effect of interventions. More attention is needed for adequate measurement definitions when reporting on and interpreting adherence or persistence estimates to multiple medications.