OBJECTIVES:

The efficiency of DM management is often compromised due to the lack of gold standard in medication adherence measurements among DM patients. This study aims to describe the available instruments used to measure medication adherence in DM.

METHODS:

A targeted literature search was performed in Medline/PubMed from 1 January 2000–19 January 2018. Search term applied were "Medication Adherence" [Mesh] and “Diabetes Mellitus” [Mesh]. Titles and abstracts of the studies were screened by two independent reviewers and selected for full-text review according to pre-defined search strategies, inclusion and exclusion criteria.

RESULTS:

The review retrieved 1,065 studies where 293 studies were finally included for qualitative synthesis after a full-text reviewed of 545 studies. Instruments used to measure medication adherence varied among the included studies. Objective measurements were employed in 52.2% of these studies which included Medication Possession Ratios (MPR) (17.7%), Proportion of Days Covered (PDC) (12.6%), pharmacy claims/refill record (3.4%), Medication Event Monitoring System (MEMS) (3.1%), and others. Subjective measurements (observer-reported or patient-reported) were utilized in 44.4% of the studies which included Morisky Medication Adherence Scale 8-item (MMAS-8) (13.0%), Morisky Medication Adherence Scale 4-item (MMAS-4) (8.9%), Summary of Diabetes Self-Care Activities (SDSCA) (2.4%) and others. There were 10 studies utilized both objective and subjective measurements to measure adherence. Biochemical measurement such as HbA1c or plasma drug level were employed as a proxy for adherence in 5 studies. Some studies attempted novel approaches such as electronic medical records and daily text messages to measure adherence. Nevertheless, MPR, MMAS-8 and, PDC remained the most commonly used measures of medication adherence in DM patients.

CONCLUSIONS:

This study reveals the inadequacy of standardization and consistency in the medication adherence measurement in DM. Therefore, more effort is required on devising a gold standard with good sensitivity and specificity in measuring medication adherence in DM.