Is There a Relationship Between Part D Medication Adherence and Part C Intermediate Outcomes Star Ratings Measures?

Improvements in the Centers for Medicare & Medicaid Services (CMS) star ratings Part D medication adherence measures may affect performance in Part C intermediate outcome measures for which the Part D targeted medication classes are prescribed.

To determine if Part D medication adherence measures are associated with corresponding Part C intermediate outcome measures.

This was a cross-sectional analysis using the CMS 2015 star ratings report (based on 2013 benefit year plan data) for Medicare contracts. The measures of interest included the Part D adherence measures for diabetes medications, antihypertensive agents, and statins and the Part C intermediate outcome measures for controlled blood sugar, blood pressure, and cholesterol. All Medicare Advantage Prescription Drug (MAPD) contracts with complete data for all Part C and D measures of interest were included. Contracts with ≥ 25% of total enrollment with MA-only benefit were excluded. Linear and logistic regression models were used to assess the association between 2015 Part D adherence measures and Part C intermediate outcome measures (n = 366). The regression models were adjusted for low-income subsidy (LIS) beneficiary enrollment and log-transformed (natural logarithm) total contract enrollment.

Bivariate linear regression models demonstrated moderate positive associations between each of the 2015 Part D adherence scores and related 2015 Part C measures that explained 27%-29% (R(2)) of variance. Including LIS and total contract enrollment in the regression models increased the R2 to 30%-36%. The multivariate logistic regression models showed that each percentage point of improvement in the 2015 Part D adherence measures was associated with a 4.13 to 4.69 greater odds of performing in the top quartile in corresponding 2015 Part C measures.

Moderate positive associations were observed between the Part D and Part C scores in the same benefit year. MAPD plans may observe improved Part C intermediate outcome measures with strategies that improve Part D medication adherence measures.

This study was conducted by MedImpact Healthcare Systems, San Diego, California, without external funding. All authors are employees of MedImpact Healthcare Systems. Erickson reports advisory board fees from Sanofi and AstraZeneca. Ta, Erickson, and Patel were responsible for study concept and design and data interpretation, with assistance from Qiu. Qiu and Ta took the lead in data collection, assisted by Erickson. Ta wrote the manuscript, which was revised by Erickson and Patel.