IMPACT OF PARTICIPANT COST-SHARE ON COMPLIANCE RATES IN PARTICIPANTS WITH DIABETES

OBJECTIVE: To retrospectively assess the impact of participant cost-share levels on medication compliance rates in participants with diabetes. METHODS: Caremark's pharmacy claims database was retrospectively analyzed to identify participants filling a prescription for an anti-diabetic drug in plans with average participant cost-sharing of < 15% (LOW) or > 30% (HIGH) in 2002. Ten age/gender categories were used to match participants in the HIGH and LOW study groups. All 2002 anti-diabetic maintenance drug claims for study participants were analyzed. Compliance rates were calculated for each therapeutic class as the medication possession ratio. Two sample t-Tests compared differences in compliance rates between HIGH and LOW groups. RESULTS: A total of 125,963 individual diabetics were identified (47.7% HIGH; 46% female; 89% >44 yrs). Overall, the mean medication compliance rates were consistently higher for the diabetics with low participant cost-share. The mean medication compliance rate for LOW was 1.00 (95% CI: 1.004, 1.008) and for HIGH was 0.90 (95% CI: 0.903, 0.907; p<. 0001). The mean medication compliance rate for females in LOW was 1.00 (95% CI: 0.999, 1.005) and in HIGH was 0.89 (95% CI: 0.890, 0.896); for males in LOW the rate was 1.01 (95% CI: 1.007, 1.012) and in HIGH was 0.91.(95%CI: 0.912, 0.917; p<.0001). Mean compliance rates were lower in the high share group in every age category. The largest difference occurred for participants 19 yrs and younger, where HIGH had a mean compliance rate of 0.98 (95% CI: 0.95, 1.02), and LOW 1.25 (95% CI: 1.21, 1.28; p<.0001). CONCLUSION: This study shows that high participant cost sharing is associated with decreased medication compliance rates for a diabetic population. While the goal of cost-sharing is to decrease total drug spending, the amount saved may not offset the effects of decreased compliance for maintenance medications in a diabetic population. More study is needed to better understand compliance and cost-sharing.