BACKGROUND: Poor adherence in COPD can increase the exacerbation risk. The GOLD 2023 guidelines recommend the assessment of adherence as a key action item. However, different methods to assess adherence exist and the chosen methodology could impact the outcome.

AIM: To systematically review literature to describe and critically evaluate the different methods used to assess adherence to COPD medication in electronic healthcare databases.

METHODS: We searched MEDLINE using the PubMed interface, Web of Science and Embase for articles published before October 11th 2022. Screening for inclusion and data extraction were independently conducted by two reviewers. Methods to assess adherence were evaluated according to ISPOR and EPSACOMP checklists.

RESULTS: A total of 161 studies were included, with 4 assessing initiation, 134 implementation and 48 papers assessing persistence (based on the ABC taxonomy of Vrijens, B. et al. BJCP 2012;73(5):691-705). Adherence was mainly assessed in outpatient dispensing data. In total, 18 different methods to assess implementation were mentioned, whereby the majority of the studies (72%, 97/134) reported (a variant of) the medication possession ratio (MPR, 40/97) or the proportion of days covered (PDC, 66/97). Diverse definitions of persistence were observed, with 31% (15/48) indicating a rationale for the chosen treatment gap. Only 14% (22/161) of all included studies incorporated hospitalization days in their formula.

CONCLUSION: Despite efforts for harmonization, variations in adherence assessment methods are widespread. Attention for transparency, the impact of hospitalization stays and the rationale in choosing an adherence measure is recommended.