Background: The study aims to critically analyze the scientific literature concerning methods for assessing medication adherence (MA), the factors that influence it, medication adherence-enhancing interventions (MAEIs), and the consequences of medication nonadherence (MNA) among rare diseases (RDs) patients.
Methods: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, a systematic search was conducted on PubMed’s electronic database until 26 January 2024, regardless of the publication year or type. All identified articles were exported to Rayyan and Mendeley software tools to remove duplicate papers. Two authors independently reviewed the selected articles to determine their relevance to the inclusion and exclusion criteria. Articles that did not provide summarized reports of MA in patients with RD, did not have full text available, sufficient information in the abstract, or an English translation were excluded. One investigator entered the study data into the extraction table, and another verified it for accuracy and completeness. A protocol has been registered on the Open Science Framework platform. The risk of bias was assessed using the Mixed Methods Appraisal Tool and the Joanna Briggs Institute tools.
Results: Twenty-nine studies met the inclusion criteria, along with 20 additional studies from our previous published scoping review. MA among patients with RD exhibited considerable variability, with prevalent assessment measures including the Morisky Medication Adherence Scale (n = 6), questionnaires (n = 7), databases/registries (n = 5), and a combination thereof (n = 5). The most common factors associated with MNA were patient- and therapy-related. Notable risks of MNA included hospital admissions and disease worsening. Educating patients and considering their preferences were the most frequently used MAEIs.
Conclusion: Efforts are crucial to ensure the timely assessment, reporting, and enhancement of MA. The lack of a specific approach adopted via the national legal framework might be recognized as one of the main factors for neglecting MNA issues in this group of patients.