As health care costs continue to rise, payers are increasingly shifting costs to patients through higher deductibles and co-payments [32
]. Yet, uniform increases in co-payments may curb the use of both low-value and high-value therapies alike, potentially resulting in adverse health consequences in individuals with chronic diseases [18
]. VBID has been proposed specifically to offset the adverse clinical effects of rising out-of-pocket costs, by setting the patient co-payment amount relative to the value – not exclusively the cost – of the therapy [28
]. While several large employers and insurers are experimenting with VBID type programs, there have been no prospective controlled evaluations of the impact of such programs in actual practice.
This trial is the first of its kind – an intervention of targeted co-payment reductions for specific high-value therapies in specific high-risk patients – designed both to improve adherence to evidence-based therapies by patients with diabetes in the workforce, but also to allow for rigorous evaluation of the program's effectiveness. The trial's progress to date has demonstrated the feasibility of implementing targeted, value-based benefit design changes in practice. The automatic opt-in design of the intervention has created near unanimous participation. No significant barriers to implementation have been encountered to date, and the intervention continues to receive strong employee-level and institutional-level support at UM. Planned analyses will determine the intervention's impact on the uptake of and adherence to evidence-based medications, as well as the impact on the use and cost of both pharmaceutical and non-pharmaceutical health services.
This study has some limitations. First, determining the effect of the co-payment reductions above any effects due to secular trends in adherence can be difficult. Second, although the control group was identified from the same health plan using the same selection criteria used to identify the intervention group, differences remain between these two groups because randomization was not part of the study design. That noted, the interrupted time series, control group design was specifically chosen because it provides a strong test of whether the copayment reductions impact on medication adherence, separate from other ongoing temporal changes in adherence or baseline differences between the two groups [34
Third, this trial is taking place in an evolving health care marketplace, which may make it more difficult to isolate the effect of the intervention from other ongoing benefit design changes or quality-improvement initiatives. Again, FOD's interrupted time series control group design offsets this concern, to the extent possible, and is a key methodological strength of the trial. By assessing outcomes for an intervention and a control group at multiple times both before and after the intervention, we capture and can control for temporal trends due to other market factors, provided they do not occur in only one of the two groups at the same time as the intervention is implemented.
Fourth, adherence is estimated using medication possession ratios, which assume that the supply of medication dispensed is an adequate proxy for patient adherence. However, because the intervention should have a direct effect on pill-buying but only an indirect effect on pill-taking, MPR is likely to modestly overestimate actual adherence, by causing some unknown number of patients to buy but not take their medications. Further, if physicians instruct patients to take medications differently than prescribed, or if medications are stockpiled or conversely lost, MPR may be an imperfect measure. However, the use of MPR as a measure of adherence for controlled trials has been validated by Steiner and colleagues and is used extensively in clinical research [45
]. Fifth, the trial focuses on individuals with diabetes with employer-based health insurance. While over 62% of the non-elderly U.S. population has employer-based coverage [46
], there is tremendous heterogeneity in employer benefit packages and in the health risk profiles of employees, potentially limiting generalizability.
Sixth, a common difficulty with any policy intervention is assessing for unintended consequences (or externalities) which may arise as a result of the intervention. To the extent we have anticipated them, we will examine for potential externalities, such as formulary tier-shifting, in which individuals shift from lower to higher tier drugs in response to the co-payment reductions. Our intervention maintained a cost advantage for using lower tiers, but the extent of tier-shifting remains an empirical issue that we will explore.
Finally, a practical issue related to the likely uptake of VBID-type interventions merits mention. With health care costs rising rapidly, payers are looking for ways to constrain cost growth, potentially limiting the appeal of benefit design alterations which shift pharmaceutical costs back to the employer from the patient. For the most part, employers want to see a positive return on investment, which is unlikely when framed solely in financial terms. However, the true return on investment in health care is health. When framed in these terms, employers should expect and even demand a positive return on investment.
In conclusion, we have described the rationale, design, and implementation of a prospective controlled trial designed to test the effectiveness of targeted, value-based co-payment reductions in improving medication adherence among a population of individuals with diabetes covered by employer-sponsored health insurance. Findings from this study should provide needed insight into the responsiveness of patients' medication-taking behaviors to targeted reductions in out-of-pocket costs, as well as the impact on both pharmaceutical and overall health care utilization and spending. This study is quite timely given rapidly rising health care costs, increasing use of consumer-directed health care (with its high cost-sharing requirements), and continuing pervasive quality gaps between the optimal use of high-value chronic disease therapies and their actual use in practice [47
]. Data from this study will provide payers with needed insights into the role of VBID to mitigate the adverse health consequences of underuse due to high out-of-pocket expenditures, while continuing to use cost-sharing to discourage overuse.