OBJECTIVES: To evaluate the impact of value-based insurance design (VBID) on adherence to diabetic medications. METHODS: Health Alliance Medical Plans of Illinois piloted VBID by placing at least one diabetic drug in each class at Tier 1 with a $10 copayment for a subgroup of 5400 enrollees in January 2007, while keeping drug benefi ts unchanged for all other plan enrollees. A matched difference in difference method (DID) was used to evaluate the effect of VBID, based on pharmacy claim data. Patients with unchanged benefi ts in the same plan were used as the control group. Patients included in the analysis needed to be continuously enrolled from January 2006 to December 2007 and have used diabetic medications in both years. Adherence was measured by the proportion of days covered (PDC). A logistic model was used to model the probability of having PDC >=0.8. A 1-to-1 matched control group was generated based on propensity score. RESULTS: There were 71 patients in the case group and 5037 patients in the control group. The matched control group had 71 patients with similar propensity score, baseline characteristics and baseline adherence level with the case group. After the implementation of VBID, the average copayment for diabetic medications decreased from $21.70 to $14.00 for the case group and increased from $19.60 to $22.00 for the matched control group. The probability of being adherent increased from 69% to 79% for the case group and decreased from 72% to 70% for the matched control group. The matched DID model showed that VBID increased the probability of being adherent: OR =1.84, 95% CI: 0.96-3.54, p =0.068. The full sample DID estimated OR =1.56 with p =0.065. CONCLUSIONS: A VBID program that reduced the copayment for diabetic medications by 35% improved the odds of adherence by 84% and reduced the number of non-adherent patients by 35%.
Zeng, F., An, J., Patel, B., Scully, R., & Barrington, C. (2009). PDB56 THE EFFECT OF VALUE-BASED INSURANCE DESIGN ON ADHERENCE TO DIABETES MEDICATIONS: A MATCHED DIFFERENCE IN DIFFERENCE EVALUATION. Value in Health, 12(3), A107. https://doi.org/10.1016/s1098-3015(10)73599-3