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

BACKGROUND: 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. OBJECTIVE: To determine if Part D medication adherence measures are associated with corresponding Part C intermediate outcome measures. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.