How Do You Best Measure Medication Adherence?
Measuring Medication Adherence Using Claims Data
Medication adherence measurement is associated with better clinical outcomes and lower healthcare costs, and therefore is an important measure in health economics and outcomes research (HEOR) studies. Medical claims data offer a rich source of information about prescription fill patterns and patient behavior, allowing researchers to evaluate adherence in different ways. Two of the most used adherence methods are:
Proportion of Days Covered (PDC)
This is a widely accepted measure of medication adherence. PDC calculates an adherence percentage by comparing the number of days a patient has access to their medication compared with the total number of days in a measurement period. For example, if a patient is prescribed a daily medication for 30 days, and the medication is available for 25 of those days, the PDC would be ((25/30) × 100), or 83.3%. A PDC of 80% or higher is often considered indicative of good adherence. Utilizing this measure of adherence requires detailed claims data on medication fills and refill dates.
Medication Possession Ratio (MPR)
Similar to PDC, MPR is another common metric that evaluates the ratio of the total days’ supply of medication dispensed to the total number of days in the observation period. Medication Possession Ratio (MPR) is calculated by dividing the sum of days’ supply of medication by the number of days in the study period. While MPR provides a useful measure, it can be less accurate than PDC because it may not account for gaps in medication use and can sometimes overestimate adherence if patients obtain refills early.
Other Adherence Measures
While PDC and MPR are the most commonly utilized medication adherence measures, other adherence measures using medical claims data may be used depending on research need. These include:
- Gap Analysis: This method identifies periods where there is a lapse in medication coverage. By analyzing the gaps between prescription fills, this approach assesses how often and for how long patients miss doses. Large gaps or frequent short gaps in medication coverage can indicate poor adherence. This method provides insights into adherence patterns over time but requires detailed tracking of refill dates and quantities
- Medication Refill Compliance: This measure assesses how consistently patients refill their prescriptions within the expected intervals. By analyzing the timing of refills relative to the expected usage patterns, healthcare professionals can infer adherence. For example, if a patient consistently refills their medication on time, it suggests good adherence. This approach can also reveal patterns of early or late refilling that may impact adherence assessments
- Complexity Index: This method involves assessing the complexity of medication regimens and their impact on adherence. Medical claims data can be used to evaluate the number of medications a patient is prescribed, their dosing schedules, and the need for multiple refills. A more complex regimen may lead to lower adherence rates, and understanding these complexities can help target interventions more effectively
Which Adherence Measure Is Right for Me?
Each of these methods has its strengths and limitations, and the choice of method can depend on the specific context and objectives of the analysis. Combining multiple measures can provide a more comprehensive understanding of medication adherence and help in devising strategies to improve patient outcomes. To learn more about how medication adherence measures can be incorporated into your studies, please contact us at Magnolia Market Access.