Prime Insights

Prime research decodes top Stars-related adherence predictors by category 

Patrick Gleason, PharmD, FCCP, BCPS | Aug. 31, 2016

In my last post, I discussed the top adherence predictors across the three medicine-related performance measures that make up nearly one-third of a Medicare plan sponsor’s Star rating. These three measures include: high blood pressure (RAS antagonists), high cholesterol (statins) and diabetes (excluding insulin). That post provided an informative, high-level view into my team’s research of more than 1.1 million Medicare members over three years, but it’s worthwhile to dive deeper.

In this post, I’ll explore some of the top adherence predictors for each medicine category. We’ll look at how they compare and contrast, and revisit our evidence-based recommendations for benefit design that can help to maximize adherence.

Variance of top adherence predictor impact across categories
Though the top adherence predictors were widely the same, the impact on adherence varied greatly across categories. Some of these predictors included:

  • Higher claims counts from the previous year
  • Lower illness severity (as defined by  Pharmacy Risk Group (PRG) score)
  • Percent of members with generic cost share of $4 or less for a 30-day supply
  • Percent of members who had an extended (90-day) supply claim in the previous year

Percent impact of adherence odds for top CMS Stars-related drug categories


Diabetes medicines (excluding insulin)

High cholesterol medicines (statins)

High blood pressure medicines (RAS antagonists)†

Previous year claim count 12+ (vs. <7)




Lower illness severity

(PRG<4.2 compared to PRG >/= 4.2)

(PRG=0 compared to PRG >/= 8)

(PRG<1.8 compared to PRG >/= 1.8)

Generic cost share of $1–$4




90-day claim in prior year




*Prior year statin adherence was found to be a predictor of RAS antagonist adherence.
**Adherent yes versus no defined as percent days covered (PDC )>/= 80% defined as adherent.

Unique predictors by category
Though many of the top adherence predictors overlapped for the three Stars-related medicine categories, there were a few differences:

  • An age of less than 76 years old was associated with higher odds of adherence for diabetes medicines.
  • Higher median household income in the member’s zip code was associated with higher odds of adherence for statins.
  • Higher high school graduation rate in the member’s zip code was associated with higher odds adherence for statins and RAS antagonists.
  • Enrollment in a Medicare Advantage Prescription Drug Plan (MAPD) was associated with higher odds of adherence for RAS antagonists.

Top recommendations for maximizing adherence through benefit design
Although individual characteristics can help plan sponsors to better understand populations and effectively target adherence interventions, they’re non-modifiable. To take action that could help to maximize outcomes, adherence and Stars-related CMS bonuses, Prime recommends taking advantage of the two actionable, benefit design opportunities supported by these findings: 

  • Set generic cost share at $4 for Stars-related drug categories.
  • Include and encourage use of extended supplies though retail, mail or both.

To learn more about this study or Prime’s collection health outcomes research, please contact us.

About Prime Therapeutics

Prime Therapeutics LLC (Prime) helps people get the medicine they need to feel better and live well. Prime manages pharmacy benefits for health plans, employers, and government programs including Medicare and Medicaid. The company processes claims and delivers medicine to members, offering clinical services for people with complex medical conditions. Headquartered in St. Paul, Minn., Prime serves just over 22 million people. It is collectively owned by 14 Blue Cross and Blue Shield Plans, subsidiaries or affiliates of those plans. Prime has been recognized as one of the fastest-growing private companies in the nation.  

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