Beyond PDC & MPR: How Dose-by-Dose Metrics Improve Quality

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Jan 26, 2022

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The problem of medication non-adherence

It’s no secret that medications are essential to ease pain, stop infectious disease, and manage chronic conditions. Yet for every medication prescribed, one goes unfilled. And of the medications picked up at the pharmacy, only half are taken correctly.1

Medication adherence, defined by the FDA as the extent to which patients take medications properly, is essential for patients to get and stay well. Medication non-adherence, as it is called, results in poor health, emergency hospital visits and stays, spread of disease, and worse.

Rarely is there a single reason why patients do not take medications as prescribed. Reasons include cost, side effects, forgetfulness, or not understanding doctor’s directions. And the responsibility for ensuring medication adherence is also diffuse: shared between physicians, patients, health plans, and the government. Non-adherence is everybody’s—and nobody’s— problem.

PDC and MPR are commonly used measures of medication adherence

Health plans, for their part, use well-established and accepted measures of medication adherence in order to meet quality measures. Plans aim to provide care that meets a variety of federal and state quality metrics, many of which are directly or indirectly influenced by adherence. Specifically, four Medicare Part D quality measures address adherence to diabetes, hypertension, and cholesterol medications2; many state-level Medicaid quality payments are also directly or indirectly related to adherence.

Unfortunately, the measuring sticks that undergird these metrics fall short. Instead of measuring true, dose-by-dose adherence, health plans and pharmacists focus on medication possession ratio (MPR) and proportion of days covered (PDC). These metrics focus exclusively on prescription refills. However, not refilling medications is just one aspect of non-adherence.

Put simply, PDC and MPR gauge what percentage of time a patient has medicines in his or her purse, bathroom, or car. Relying on pharmacy claims, they tell us whether or not a prescription has been filled on time.  In fact, a patient could receive all of their medications by mail, take not a single dose, and receive a perfect score on this metric. And as pharmacy industry observers ask:

“…are we measuring adherence with MPR and PDC, or are we measuring refill behavior?”
MPR and PDC don’t really tell us how patients take their medications day in and day out (or day on and day off). Is the patient taking it in the correct amount at the right time with the right frequency and under the right conditions? MPR and PDC can’t tell you that.
Pharmacy Times, “Direct Medication Adherence Measures Available With Technology.”

What’s more, MPR and PDC are lagging indicators. They are not timely enough to give information to guide an intervention.

We can do better. We can marry indirect measures with human-powered technology that gives us the accuracy of direct, dose-by-dose observation with impactful interventions.

New technology for assessing true adherence

Directly Observed Therapy (DOT) has always been the gold standard for supporting medication adherence. DOT is exactly what it sounds like: a trained observer, such as a nurse or health coach, engages with patients to support them in taking their medication properly. Coaches answer questions and provide tips to ensure technique, timing, and dose are correct and barriers such as side effects are identified and resolved.  

DOT is used for medication administration for all hospitalized patients. In the outpatient setting, DOT is also used for treatment of tuberculosis by our public health departments. When delivered by nurses in the school setting, DOT reduces children’s asthma exacerbations.

Until now, DOT has not been used more broadly because it has been considered too resource- and time-intensive to scale. However, when we pair DOT with video-enabled human support, it becomes scalable and available to larger groups of patients, outside of the clinic walls.

How video-enabled dose-by-dose adherence provides more accurate measurement than MPR or PDC

Video-enabled DOT is much more accurate than MPR or PDC for gauging real adherence and can do so quickly enough to support interventions, when appropriate. It can reveal not only whether patients are taking medication as prescribed, but also why patients either miss doses of medication or fail to administer medication properly. More importantly, it can allow for timely intervention to improve adherence quickly, resulting in better outcomes.

Patient support can include asynchronous two-way chats or videos with an adherence coach, help from a pharmacist, live video visits, or even guidance on changing medications.

Finally, video DOT works for patients. Technology, paired with the care of a human touch, works with patients’ schedules and lets them record, store, and share information. Patients are more engaged when they have a chance to share and consume video information on their own schedule, in their own way.

Why combining MPR, PDC and dose-by-dose measures supports better outcomes

If the goal of measuring medication adherence is to improve human health, we should complement PDC and MPR with dose-by-dose adherence metrics.

PDC and MPR are well-established measures of medication refill behavior and as such, are an essential first step in understanding if patients can obtain their medications, on schedule.

But if we combine this widely-available data with actual proof of medication adherence, providers will know how well patients are truly doing with their medications. In addition, patients will receive the support they need to stay adherent.  

The great news is that with new technology, measurement of direct adherence is now possible, affordable, and reimbursable.  

1 The Cost of Medication Non-Adherence




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