A framework for understanding sources of bias in medication adherence research

The sources of bias in medication adherence research have not been comprehensively explored. We aimed to identify biases expected to affect adherence research and to develop a framework for mapping these onto the phases of adherence (initiation, implementation and discontinuation). A literature search was conducted, key papers were reviewed and a Catalogue of Bias was consulted. The specific biases related to adherence measurement and metrics were mapped onto the phases of adherence using a tabular matrix. Twenty-three biases were identified, of which 11 were specifically relevant to adherence measures and metrics. The mapping framework showed differences in the numbers and types of biases associated with each measure and metric while highlighting those common to many adherence study designs (e.g., unacceptability bias and apprehension bias). The framework will inform the design of adherence studies and the development of risk of bias tools for adherence research.

Measuring Medication Adherence in a Population-Based Asthma Administrative Pharmacy Database: A Systematic Review and Meta-Analysis

Background

Limited studies have systematically reviewed the literature to identify and compare the various database methods and optimal thresholds for measuring medication adherence specific to adolescents and adults with asthma. In the present study, we aim to identify the methods and optimal thresholds for measuring medication adherence in population-based pharmacy databases.

Methods

We searched PubMed, Embase, International Pharmaceutical Abstracts (IPA), Web of Science, Google Scholar, and grey literature from January 1, 1998, to March 16, 2021. Two independent reviewers screened the studies, extracted the data, and assessed the quality of the studies. A quantitative knowledge synthesis was employed.

Results

Thirty-eight (38) retrospective cohort studies were eligible. This review identified 20 methods for measuring medication adherence in adolescent and adult asthma administrative health records. Two measures namely the medication possession ratio (MPR) and proportion of days covered (PDC) were commonly reported in 87% of the literature included in this study. From the meta-analysis, asthma patients who achieved adherence threshold of "0.75-1.00" [OR: 0.56, 95% CI: 0.41 to 0.77] and ">0.5" [OR: 0.71, 95% CI: 0.54 to 0.94] were less likely to experience asthma exacerbation.

Conclusion

Despite their limitations, the PDC and the MPR still remain the most common measures for assessing adherence in asthma pharmacy claim databases. The evidence synthesis showed that an adherence threshold of at least 0.75 is optimal for classifying adherent and non-adherent asthma patients.

Refill Adherence Measures and Its Association with Economic, Clinical, and Humanistic Outcomes Among Pediatric Patients: A Systematic Review

Although refill adherence measures (RAMs) are widely reviewed on their use among adult patients, existing reviews on adherence among children have only focused on self-report measures and electronic monitoring. Hence, this systematic review aims to examine the use of RAMs and their association with economic, clinical, and humanistic outcomes (ECHO) among pediatric patients. A literature search was conducted in Pubmed, Embase, CINAHL, and PsycINFO. Studies published in English involving subjects aged ≤18 years were included if RAMs were analyzed with ECHO. Of the 35 included studies, the majority (n = 33) were conducted in high-income countries. Asthma was the most common condition (n = 9) studied. Overall, 60.6% of 33 clinical outcomes reported among 22 studies was positive (improved clinical outcomes with improved adherence), while 21.9% of 32 economic outcomes reported among 16 studies was positive (reduced healthcare utilization or cost outcomes with improved adherence). Only four studies evaluated the relationship of adherence with 11 humanistic outcomes, where the majority (72.7%) were considered unclear. RAMs are associated with ECHO and can be considered for use in the pediatric population. Future studies could explore the use of RAMs in low-income countries, and the association of RAMs with quality of life.

Comparison of the predictive performance of adherence measures for virologic failure detection in people living with HIV: a systematic review and pairwise meta-analysis

A critical feature of an adherence assessment tool is its ability to predict virologic failure in people living with HIV (PLHIV). We, therefore, aimed to compare the predictive performance of commonly used adherence measures. We systematically searched MEDLINE, Embase and LILACS up to February 2018, to identify relevant observational studies comparing the effects of any two of the following adherence measurements on virologic outcomes: electronic monitoring, pill count, pharmacy refill, self-report and physician assessment. We analyzed data by pairwise meta-analyzes with a random-effects model. The proportion of virologic failures among non-adherent participants in each adherence measure was used to calculate the odds ratio (OR), with 95% Confidence Intervals (95%CI). Heterogeneity was assessed, with potential causes identified by sensitivity and subgroup analysis. We included 38 studies with individual patient data for 18,010 patients. All possible comparisons between pairs of the five adherence measures were considered and a total of nine comparison groups could be established. Meta-analysis suggested that self-report was a better predictor of virologic failure than pill count when the recall period was within one week (OR: 2.35, 95%CI: 1.07-5.18, p = 0.03). Physician assessment had higher odds of predicting virologic failure than did either self-report (OR: 2.63, 95%CI: 1.37-5.26, p < 0.01) or pharmacy refill (OR: 3.57, 95%CI: 1.69-7.14, p < 0.001). There was no difference in the predictive performance between any of the other measures that we were able to compare (p > 0.05). The combination of multiple measures did not increase the predictive value when compared to any of the measures alone. Low-cost and simple adherence measures such as self-report predict virologic failure better than or equally well as objective measures. Our results suggest that there is no need to use expensive or time-consuming adherence measures when the objective is to identify PLHIV at risk of treatment failure.

Advancing the Science and Practice of Medication Adherence

Medication adherence remains a significant unmet challenge for optimizing patient outcomes. Recent advances in the conceptualization, measurement, and support of medication adherence offer fresh opportunities to make a meaningful impact on adherence-related behavior and outcomes. These advances emphasize the multifaceted and dynamic nature of medication adherence, provide novel methods for monitoring medication adherence in clinical care, and articulate a set of multilevel strategies to more effectively improve and sustain medication adherence. Here, we offer recommendations for how clinicians can better engage with, and benefit from, these innovations to improve patient medication adherence and associated treatment outcomes.

Impact of hospitalization on medication adherence estimation in claims data

WHAT IS KNOWN AND OBJECTIVE

Pharmacy claims are commonly used to assess medication adherence. It is unclear how different approaches to handling hospitalizations compare to the gold standard of using outpatient and inpatient drug data. This study aimed to compare the impact of different approaches to handling hospitalizations on medication adherence estimation in administrative claims data.

METHODS

We identified β-blocker initiators after myocardial infarction (MI) and statin initiators regardless of hospitalization histories in the population-based, Taiwan database, which includes outpatient and inpatient drug claims data. Adherence to β-blockers or to statins during a 365-day follow-up period was estimated in outpatient pharmacy claims using the proportion of days covered (PDC) in three ways: ignoring hospitalizations (PDC1); subtracting hospitalized days from the denominator (PDC2); and assuming drug use on all hospitalized days (PDC3). We compared these to an approach that incorporated inpatient drug use (PDC4). We also used a hypothetical example to examine variations across approaches in several scenarios, such as increasing hospitalized days.

RESULTS AND DISCUSSION

Mean 365-day PDC was 74% among 1729 post-MI β-blocker initiators (range: 73.1%-74.9%) and 44% among 69 435 statins initiators (range: 43.5%-44.0%), which varied little across approaches. Differences across approaches increased with increasing number of hospitalized days. For patients hospitalized for >28 days, mean difference across approaches was >15%. PDC3 consistently yielded the highest value and PDC1 the lowest.

WHAT IS NEW AND CONCLUSIONS

On average, different approaches to handling hospitalizations lead to similar adherence estimates to the gold standard of incorporating inpatient drug use. When patients have many hospitalization days during follow-up, the choice of approach should be tailored to the specific setting.

Coming full circle in the measurement of medication adherence: opportunities and implications for health care

There is little debate that medication nonadherence is a major public health issue and that measuring nonadherence is a crucial step toward improving it. Moreover, while measuring adherence is becoming both more feasible and more common in the era of electronic information, the reliability and usefulness of various measurements of adherence have not been well established. This paper outlines the most commonly used measures of adherence and discusses the advantages and disadvantages of each that depend on the purpose for which the measure will be used. International consensus statements on definitions and guidelines for selection and use of medication adherence measures were reviewed. The quality of recommended measures was evaluated in selected publications from 2009 to 2014. The most robust medication adherence measures are often ill suited for large-scale use. Less robust measures were found to be commonly misapplied and subsequently misinterpreted in population-level analyses. Adherence assessment and measurement were rarely integrated into standard patient care practice patterns. Successful scalable and impactful strategies to improve medication adherence will depend on understanding how to efficiently and effectively measure adherence.

Novel Adherence Measures for Infusible Therapeutic Agents Indicated for Rheumatoid Arthritis

BACKGROUND

Published studies on adherence to biologic medications show that many types of calculation methods are used. However, infused biologics are not well-suited to typical measures of adherence, such as proportion of days covered.

OBJECTIVE

To construct and assess 7 novel adherence measures potentially applicable to infusible biologic agents and compare outcomes for 2 infusible biologics used for the treatment of patients with rheumatoid arthritis (RA).

METHODS

Adults (aged ≥18 years) diagnosed with RA (ie, 2 or more 714.x claims) who received ≥24 months of continuous medical and pharmacy eligibility and who started taking abatacept or infliximab therapy were selected from a large commercial insurer database of medical and pharmacy claims. The 7 new adherence measures included cumulative amount of time with a refill gap ≥20% (CG20) beyond the expected infusion interval, cumulative time off treatment, days of uninterrupted use (DoUU), observed versus expected refill ratio (OvERR), repeated observations of underuse (RoUU), variance in time between infusions, and time to discontinuation (TTD). Mean observed infusion intervals were calculated and served as a reference measure of adherence.

RESULTS

The mean maintenance intervals approximated recommended guidelines. The mean observed infusion interval for abatacept recipients was 33 days (recommended, 28 days); it was 53 days (recommended, 56 days) for patients receiving infliximab. Three measures demonstrated a significant positive relationship to the mean observed infusion interval-CG20 (r = .258), DoUU (r = .212), and TTD (r = .081; P <.05). OvERR (r = -.072) and RoUU (r = -.189; P <.05) showed significant negative correlations. Real-world comparisons showed that adherence was significantly (P <.001) greater for the infliximab group according to most measures.

CONCLUSION

New measures of adherence correlate significantly with mean maintenance intervals. Future studies should examine relationships between these adherence measures and clinically relevant end points and/or cost outcomes to determine their predictive utility. Alternative methods of reporting adherence may have greater clinical significance than traditional measures.

Adherence in the CAPRISA 004 tenofovir gel microbicide trial

High adherence is key to microbicide effectiveness. Here we provide a description of adherence interventions and the adherence rates achieved in the CAPRISA 004 Tenofovir gel trial. Adherence support for the before-and-after dosing strategy (BAT 24) was provided at enrolment and at each monthly study visit. This initially comprised individual counselling and was replaced midway by a structured theory-based adherence support program (ASP) based on motivational interviewing. The 889 women were followed for an average of 18 months and attended a total of 17,031 monthly visits. On average women reported five sex acts and returned 5.9 empty applicators per month. The adherence rate based on applicator count in relation to all reported sex acts was 72.2 % compared to the 82.0 % self-reported adherence during the last sex act. Adherence support activities, which achieve levels of adherence similar to or better than those achieved by the CAPRISA 004 ASP, will be critical to the success of future microbicide trials.

Impact of a pharmaceutical care program on clinical evolution and antiretroviral treatment adherence: a 5-year study

BACKGROUND

Antiretroviral treatments (ART) form the basis of adequate clinical control in human immunodeficiency virus-infected patients, and adherence plays a primary role in the grade and duration of the antiviral response. The objectives of this study are: (1) to determine the impact of the implementation of a pharmaceutical care program on improvement of ART adherence and on the immunovirological response of the patients; and (2) to detect possible correlations between different adherence evaluation measurements.

METHODS

A 60-month long retrospective study was conducted. Adherence measures used were: therapeutic drug monitoring, a simplified medication adherence questionnaire, and antiretroviral dispensation records (DR). The number of interviews and interventions related to adherence made for each patient in yearly periods was related to the changes in the adherence variable (measured with DR) in these same yearly periods. The dates when the laboratory tests were drawn were grouped according to proximity with the study assessment periods (February-May, 2005-2010).

RESULTS

A total of 528 patients were included in the study. A significant relationship was observed between the simplified medication adherence questionnaire and DR over the 60-month study period (P < 0.01). Improvement was observed in the mean adherence level (P < 0.001), and there was a considerable decrease in the percentage of patients with CD4+ lymphocytes less than 200 cells/mm(3) (P < 0.001). A relationship was found between the number of patients with optimum adherence levels and the time that plasma viral load remained undetected. The number of interviews and interventions performed in each patient in the first 12 months from the onset of the pharmaceutical care program (month 6), was related to a significant increase in adherence during this same time period.

CONCLUSION

The results suggest that the establishment and permanence of a pharmaceutical care program may increase ART adherence, increase permanence time of the patient with undetectable plasma viral loads, and improve patients' lymphocyte count.