Medication adherence refers to the extent to which a patient takes their medication according to the prescribed dosage, frequency, and duration. Following this regimen is an important factor in managing chronic diseases such as diabetes and hypertension, as correct use can control symptoms and prevent complications. Poor adherence can lead to diminished therapeutic effects and an increase in hospitalizations, making the consistent use of medicines a component of effective healthcare.
How Medication Adherence is Measured
Measuring medication adherence involves both direct and indirect methods. Direct methods, which are less common in practice, include observing a patient taking a dose or measuring a drug’s concentration in a blood sample. Newer approaches involve technologies like smart pill bottles that record when they are opened or ingestible sensors that signal when a pill has been consumed.
The most common way to measure adherence is through indirect methods that analyze pharmacy claims data. These methods do not confirm ingestion but provide data on how often a patient has access to their medication. Two standard metrics are the Medication Possession Ratio (MPR) and the Proportion of Days Covered (PDC).
MPR calculates the total days’ supply a patient received over a period and divides it by the number of days in that period. A limitation is that it can result in a value over 100% if a patient refills early, which can inflate the perception of adherence. This led to the preference for the PDC metric, which is a more accurate measure.
PDC also calculates the percentage of days a patient has medication available but handles overlapping refills differently. It adjusts the start date of a new refill to the day after the previous supply runs out, ensuring the ratio cannot exceed 100%. This method provides a more precise picture of continuous therapy and is endorsed by organizations like the Pharmacy Quality Alliance.
Sources of Adherence Data
Medication adherence data is collected from several points within the healthcare system. The primary source is retail and mail-order pharmacies, which generate a record every time a prescription is dispensed. This dispensing data includes the drug name, fill date, and days’ supply.
These individual pharmacy records are transmitted to larger entities that process healthcare claims. Pharmacy Benefit Managers (PBMs), which manage prescription drug benefits for health plans, compile vast databases of dispensing events. Health insurance plans also collect this information as they process claims for payment.
Healthcare providers and health systems also contribute to the data. Clinicians may ask patients about their medication habits and document this in the electronic health record (EHR). Some health systems integrate pharmacy claims data into their EHRs, giving providers a more complete view of refill histories. Digital health companies have also become a source, offering apps and smart devices for patients to self-report or automatically track medication access.
Applications of Adherence Data
One of the most direct applications of adherence data is in clinical practice, helping providers identify patients struggling with their medication regimens. Pharmacists and physicians can use this data, often as a PDC score, to flag individuals not refilling prescriptions on time. This allows for timely interventions, such as patient counseling, simplifying a regimen, or setting up automatic refill reminders.
Health systems and insurance plans use aggregated adherence data for population health management. By analyzing trends across thousands of patients, they can identify common barriers to adherence and develop targeted support programs. For example, if data shows a particular medication has low adherence rates, an organization might launch an educational campaign to address common side effects or cost concerns.
Researchers use adherence data to study the real-world effectiveness of medications. Clinical trials show how a drug performs under ideal conditions, but adherence data reveals how well it works in the everyday lives of patients. This information helps in understanding a treatment’s true impact on public health. Insurance plans and PBMs also use adherence scores as a performance metric to evaluate the quality of care provided by healthcare networks.
Patient Privacy and Data Security
The handling of medication adherence information is governed by federal regulations to protect patient privacy. The Health Insurance Portability and Accountability Act (HIPAA) establishes national standards for protecting Protected Health Information (PHI), which includes any data that can identify a patient. Pharmacies, health insurance plans, and most healthcare providers are considered “covered entities” under HIPAA and must comply with its rules.
Under HIPAA’s Privacy Rule, these covered entities cannot use or share a patient’s PHI without their consent for any purpose outside of treatment, payment, and healthcare operations. For instance, a pharmacy can share refill data with an insurance plan to process a claim, and a doctor can review that data to manage treatment. Sharing that same data with a third party for marketing would require explicit patient authorization.
For uses outside of direct patient care, such as research or population health analysis, data is typically de-identified. This process involves removing specific identifiers, like name and address, so the information cannot be traced back to an individual. By using aggregated or de-identified datasets, researchers and health systems can analyze adherence trends without compromising the privacy of individual patients.