Some reflections concerning the assessment of patient adherence and persistence to medication

The systematic review by Forbes et al.¹ compares methods for the measurement of patient persistence and adherence to medication. The results presented and discussed by the authors¹ deserve reflection, given the importance of this issue.

It is well known that evaluating adherence is not an easy task, for two major reasons: (1) Adherence is a multifactorial phenomenon, which involves more than just the simple act of taking the medication as prescribed. It implies behavior, in the broader sense, influenced by the social context of the patient as well as his/her personal knowledge, skills, motivation, and resources. Factors related to the disease, treatment, prescriber, and healthcare system can also influence adherence. All these factors should be considered to quantify and improve adherence and/or persistence. A multidisciplinary team supporting patient empowerment and devoting enough time to him/her, especially in the case of patients with complex regimens or polypharmacy, is required². (2) Several methodologies are available to assess patient adherence and/or persistence, but there is no single ‘gold standard’. Each method has its pros and cons, and its value may depend on the setting and the aims of the evaluation, as well as on the resources available or the drug characteristics. Given these considerations, there is ample evidence that the estimation of adherence and persistence should be based on a combination of methods³. Preferably, one standard and validated method and another one specifically designed to measure adherence at patient level⁴.

Pharmacy and medical records, as well as pill count and electronic monitoring (e.g. enabled with Medication Event Monitoring Systems, MEMS), are considered the most objective and accurate methods for the assessment of adherence/persistence¹. The use of the first two has become widespread in recent years, thanks to the increased availability of administrative health records which are valuable research tools. They allow access to large-population pharmaceutical and/or clinical data on real-world use and allow long-term study. Nevertheless, their use for measuring adherence and/or persistence raises doubts about the type of calculation used. In this context, the Proportion of Days Covered (PDC) may be a more precise indicator than the Medication Possession Ratio (MPR), especially for long-term treatments, given that it does not over-estimate adherence when overlapping, and that it is closer to the concept of persistence³. MPR is a sum of days. In the MPR calculation, a patient who refills a medication 7 days prior to running out of it will have overlapping days supplied, which would elevate MPR. In this way, days in which more than a drug is used are counted only once. Considering each prescription of an array of days supplied, before evaluating PDC, overlapping arrays are moved forward to the first day that the patient would not have medication. Moving these arrays forward provides a true picture of the days on which a patient is “covered” with medication, rather than a simple summation of all days supplied with MPR.

With the objective of making progress on uniformity in the terminology and measurements used to quantify medication adherence from medical records, the European Ascertaining Barriers for Compliance (ABC) project⁵ has proposed a new taxonomy to define some standards and modus operandi. In this context, the European Society for Patient Adherence, COMpliance, and Persistence (ESPACOMP) developed the ESPACOMP Medication Adherence Reporting Guidelines (EMERGE) that consider the ABC taxonomy of medication adherence as a conceptual basis, and provide detailed guidance on reporting adherence data in a transparent, complete, and comparable way⁶. Inter alia, this guideline suggests that, together with adherence, persistence should be described to provide a more complete representation of drug utilization. There is, in fact, increasing evidence that adherence as a process must be assessed over time and not just at one point in time. Moreover, chronic disease management requires a continuous and adaptable attention that may influence outcomes. Therefore, adherence assessment in older patients, most of them multi-morbid and polymedicated, should include discontinuation of therapy rather than just isolated daily adherence.

The assessment of adherence and/or persistence in polymedicated patients, for whom their social context plays an even more important role, is complex and requires special attention. Some authors⁷ have described the limitations in detail. In broad terms, the indicators designed and widely used to evaluate single-medication adherence or persistence are not valid for this assessment; it has been shown⁷ that they tend to over- or under-estimate them. Therefore, the existing methods of calculation must be adapted to each specific case of polypharmacy. Further research is needed in this respect.

Medication adherence plays an important role in the effectiveness of drugs. In the frequent context of trying to describe the effectiveness of treatment in a multimorbid patient, in addition to methodological constraints, the question of whether assessing adherence is a priority must be raised. In such a scenario, it is desirable that, once the need for a treatment has been determined, the patient must understand and, then, independently accept the situation. Only then can the proposed scheme be drawn up together with the patient, and the consequences of poor disease control or a lack of adherence need to be well understood. This makes it more likely that the patient will adhere to the therapy, in contrast to those whose drug regimen is imposed unilaterally by the prescriber.

In accordance with the above, and within the framework of the renovated Action Plan 2016–2018 in the European Innovation Partnership on Active and Healthy Ageing (EIP on AHA), the group on “Adherence to prescription and medical plans” promotes a holistic approach to adherence. They advocate the provision of more information to patients, especially the elderly, on pharmacological treatments and with chronic diseases. This fosters collaborative outcomes between healthcare professionals and improves their communication skills in their relations with patients and caregivers, as well as disseminating the results among policy-makers⁸.

In conclusion, it is not possible to fully evaluate medication adherence without specifying the context, in terms of which kind of disease and patient we are referring to. When, how, and for what should always be asked first.

Transparency

Declaration of financial/other relationships

E. Menditto, and P. Kardas are co-coordinators (EM) or promoters (PK) of Action Group A1 “Prescription and adherence to treatment” of the European initiative European Innovation Partnership on Active and Healthy Ageing (EIP-AHA). All work carried out by the partners of the EIP on AHA is purely on a voluntary basis. The authors report no other conflicts of interest in this work. CMRO peer reviewers on this paper have no interests to disclose.

Acknowledgements

None reported.

Additional information

Funding

This commentary was not funded.