Measuring Adherence to Multiple Medications Using Guideline-Directed Medical Therapy as a Model

Area of Science:

• Cardiology
• Pharmacoeconomics
• Health Services Research

Background:

• Heart failure (HF) management necessitates complex medication regimens, termed guideline-directed-medical therapy (GDMT).
• Assessing adherence to multiple HF medications is challenging due to the lack of a gold standard.
• Proportion of days covered (PDC) is a common metric for medication adherence.

Purpose of the Study:

• To compare seven different Proportion of Days Covered (PDC) measures for assessing adherence to multiple guideline-directed-medical therapy (GDMT) medications in heart failure (HF) patients.
• To evaluate the association between these various PDC adherence measures and clinical outcomes.

Main Methods:

• A retrospective cohort study included 34,603 heart failure patients who filled GDMT prescriptions between April 2021 and July 2022.
• Seven PDC-based adherence measures were derived from electronic health record and pharmacy data.
• Clinical outcomes included emergency department visits, hospitalizations, and death.

Main Results:

• A wide range of adherence was observed across the seven PDC measures, from 54% with the strictest ('each') to 73% with the least restrictive ('at least one') measure.
• Adherence variability increased with a higher number of GDMT medications.
• Higher PDC across all measures was associated with an increased number of emergency department visits, hospitalizations, and death.

Conclusions:

• The choice of Proportion of Days Covered (PDC) measure significantly impacts the assessment of medication adherence in heart failure patients on guideline-directed-medical therapy (GDMT).
• This variability has substantial implications for policy, clinical practice, and intervention strategies.
• Further research is needed to establish a standardized and validated approach for measuring multi-medication adherence.