Improving the assessment of medication adherence: Challenges and considerations with a focus on low-resource settings

Improving patient survival and quality of life in chronic diseases requires prolonged and often lifelong medication intake. Less than half of patients with chronic diseases globally are adherent to their prescribed medications which preclude the full benefit of treatment, worsens therapeutic outcomes, accelerates disease progression, and causes enormous economic losses. The accurate assessment of medication adherence is pivotal for both researchers and clinicians. Medication adherence can be assessed through both direct and indirect measures. Indirect measures include both subjective (self-report measures such as questionnaire and interview) and objective (pill count and secondary database analysis) measures and constitute the mainstay of assessing medication adherence. However, the lack of an inexpensive, ubiquitous, universal gold standard for assessment of medication adherence emphasizes the need to utilize a combination of measures to differentiate adherent and nonadherent patients. The global heterogeneity in health systems precludes the development of a universal guideline for evaluating medication adherence. Methods based on the secondary database analysis are mostly ineffectual in low-resource settings lacking electronic pharmacy and insurance databases and allowing refills without updated, valid prescriptions from private pharmacies. This significantly restricts the choices for assessing adherence until digitization of medical data takes root in much of the developing world. Nevertheless, there is ample scope for improving self-report measures of adherence. Effective interview techniques, especially accounting for suboptimal patient health literacy, validation of adherence questionnaires, and avoiding conceptual fallacies in reporting adherence can improve the assessment of medication adherence and promote understanding of its causal factors.