84 ComputerTalk

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Calculating PDC requires specific start and stop dates for the mea-surement, making it more suited to situations where patients started therapy at the same time rather than on different days. It also disregards treatment gaps. The calculation for PDC is:

PDC = Number of days with drug on hand Number of days in a specified time interval

Prescriptions filled during the speci-fied interval are evaluated using a set of rules to avoid double-counting of days. Unlike with MPR, these rules limit the PDC to values between 0

Measuring the Impact of Medication Adherence Programs

In the last issue of ComputerTalk we discussed programs designed to help increase medication adherence. As you consider how to improve medication adherence at your pharmacy, we’d like to explain ways you

can measure the impact of your program, and share with you an important reason why now is the time to focus on adherence. Medication adherence can be measured in a variety of ways, from patient interviews to analyzing retrospective claims data. Two common metrics used to calculate patient adherence based on prescription refill data are medication possession ratio (MPR) and proportion of days covered (PDC). These metrics are appropri-ate for measuring adherence for long-term treatment medications. Adher-ence to acute use or as-needed medications, and prescriptions with less than a 30-day supply, cannot be assessed using MPR or PDC calculations.

MPR requires at least two fill dates to calculate the ratio. The calculation for MPR is:

MPR = Number of days supplied within refill interval Number of days in refill interval

The last refill is not included in the calculation, leaving the refill interval to contain the days between the first fill and last refill. The ideal MPR is 1, indicating 100% medication adherence. An MPR value of greater than 1 (better-than-“perfect” adherence) may occur if patients refill prescriptions before they run out of medication if patients are overusing medication, or it may indicate bad data.

Using the MPR calculation may over or under estimate adherence, since it does not take into account treatment gaps, changes in therapy, or the num-ber of days in the interval between the first and last refill. Some studies have modified the MPR equation to account for this limitation:

MPR= Days’ supply of medication available to patient Number of days patient had medication + days’ supply of last fill

Melissa Sherer Krause, Pharm.D.

Ashley Gibbons, Pharm.D.

Learn MorePharmacy Quality Alliance www.pqaalliance.org

National Community Pharmacists Association www.ncpanet.org

National Alliance of State Pharmacy Associationswww.naspa.us

85March/April 2012

and 1. Table 1 depicts the calculation of MPR and PDC for the same set of claims data. Table 2 illustrates this ex-ample of PDC, which is calculated for a specified time interval of October 1, 2011, through February 29, 2012 (152 days).

As these examples show, MPR and PDC can result in similar, but not necessarily identical, measures of medication adherence for the same data set. Neither calculation is “right” or “wrong.” All methods of calculating adherence have limitations.

To compute MPR or PDC measure-ments at your pharmacy, we suggest you look at your pharmacy system reporting capabilities, find reports showing longitudinal patient usage at the patient level, export the data into Microsoft Excel, and create formulas to calculate MPR and PDC as we have done above.

Prescription claims data can never tell the whole story of a patient’s adherence. Patients must consistently use the same pharmacy to fill their medications, or the data will be in- continued on next page

Table 2. Medication fill pattern. Adapted from “Calculating Medication Compliance, Adherence, and Persistence in Administrative Pharmacy Claims Databases.” R. Scott Leslie. www.wuss.org/proceedings08/ 08WUSS%20Proceedings/papers/anl/anl09.pdf.

MPR

Fill Date Days’ Supply

Total Days’ Supply

Total Number of Days MPR

10/1/2011 30 120 160 0.75

11/3/2011 30 12/28/2011 30

2/2/2012 30

3/8/2012 30

PDC

Fill Date Days’ Supply

Number of Days with

Drug On Hand

Interval of Days (10/1/2011–2/29/2012)

PDC

10/1/2011 30 118 152 .7811/3/2011 30

12/28/2011 302/2/2012 30

3/8/2012 30

Medication Fill Pattern in Five-Month Period

Table 1. MPR and PDC for the same set of claims data.

complete. Even knowing fill records does not ensure that patients are taking their medication as pre-scribed, or even at all. Observed utilization often does not corre-spond to actual utilization.

What Does “Good” Look Like? The desired adher-ence standard used by most studies is 0.80, or 80%, although this value does not necessarily equate to opti-mal adherence in all disease states.

86 ComputerTalk

Cardiovascular conditions have shown that adherence of 80% and greater significantly improves outcomes. How-ever, adherence rates of only 80% would not be sufficient for medications such as antiretroviral treatment and oral contraceptives. Studies have shown that HIV patient adherence of less than 95% is associated with higher risks of treatment failure. To put the numbers in perspec-tive, an adherence rate of 80% means that a patient on a once-daily treatment would be missing more than one dose a week during a one-month time period.

Why Focus on Adherence? 2012 Medi-care Part D Star Ratings One particular reason to focus on medication adherence now comes from the Centers for Medicare and Medic-aid Services (CMS), which is evaluating and reporting on Medicare Part D plans through a 1-to-5-star rating system. The ratings are used in several ways, including quality-based payments to Medicare Advantage plans (MA-PDs) and marketing benefits to prescription drug plans (PDPs). Star ratings are assigned based on perfor-mance in four domains. One of these domains, drug pricing and patient safety, includes medication adherence

measures for oral diabetes medications, hypertension medication (ACEI and ARB), and cholesterol medication (statins).

CMS has chosen to measure medication adherence using PDC, as recommend by the Pharmacy Quality Alliance (PQA). CMS has chosen to use the “standard” 80% or greater adherence as a cutoff to identify patients with high adherence. Reports released in October 2011, showed average rates for Medicare Part D plans fell be-low “high adherence” values. Average PDC calculations for MA-PDs ranged from 68% for statins to 72.2% for ACEI/ARBs to 73.0% for oral diabetes medications.

In February, CMS announced that some of the cal-culations in the area of medication adherence for oral

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Index of Advertisers

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87March/April 2012

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diabetes medications (DM-ADH) needed to be revised. Patients who had only one claim of a combination diabetes drug were “erroneously included in this mea-sure; one claim of a combination drug was incorrectly counted as two separate fills.” These patients were considered nonadherent when they should have actually been excluded from the calculation of adherence. The revised calculations provide a higher level of adherence to oral diabetes medications than originally reported. CMS stated that the majority of changes are less than one percentage point.

PDPs experienced a smaller impact as a result of the revised calculations, though a higher percentage of PDPs were affected. Over three-fourths of the 70 PDPs (53 out of 70) had an increase in their calculated DM-ADH, but this did not change any of the PDPs’ star ratings for this measure or their overall rating.

What Does It Mean for Pharmacy? While the revised calculations brighten somewhat the picture for medication adherence in the area of diabetes medications, the fact remains that adherence in all three categories is far from perfect. As

Robert Coopman astutely pointed out in an article in Chain Drug Review last fall, MA-PDs “cannot achieve the five-star rating without active and effective participation from community pharmacies that create quality patient outcomes.” He suggests that pharmacy chains get involved with the PQA in their ef-forts to identify measures of medication use quality. We would urge all pharmacies, especially independent phar-macies, to join the movement by working with PQA, the National Community Pharmacists Association (NCPA), and/or your state pharmacy association. And as we pointed out in the last issue of ComputerTalk, continue to focus on medication adherence initiatives at your pharmacy. Collect data and analyze the performance of your medication adherence efforts so you know what’s working so you can refine your approach. CT

Ashley Gibbons, Pharm.D., and Melissa Sherer Krause, Pharm.D., are consultants with Pharmacy Healthcare Solutions, Inc., (PHSI), in Pittsburgh, Pa., which provides consulting solu-tions that improve the profitability of its healthcare clients. For more information on these calculations, please contact Ashley at agibbons@phsirx.com or Melissa at mkrause@phsirx.com. The authors would like to thank Alison Huet, Pharm.D. candidate for 2012 from Ohio Northern University, for her assistance.

2012 Quick refence TAbles: SpeCifiC interfaCeS Offered

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