Do Drugs Save Money? A Plausibility Test

In a previous post, I commented on a study that examined the correlation between medication compliance and use of other healthcare services over three years for a large population of commercially insured members with a diabetes or cardiovascular-related diagnosis.  The study found a strong association between greater medication adherence (defined as a medication possession ratio of 0.80 or higher) and lower utilization of other medical services, primarily hospitalizations.  Considering all healthcare costs, not just disease-related, they reported an ROI of 3:1 for medication adherence in dyslipidemia and 10:1 for hypertension.

While my previous post highlighted a key methodological concern about the study, one of the most powerful tools for quickly stress-testing a study’s findings is to conduct a plausibility test to see if the results match up with what other rigorous research would suggest.   For this plausibility comparison, I selected a meta-analysis of data from 90,056 individuals in 14 randomized trials of statins.  There are other meta-analyses and randomized controlled trials that I could have chosen, which would have led to similar conclusions.

The adherence study included all patients with dyslipidemia as evidenced by a diagnosis in the medical claims.  To be conservative, I selected patients from the meta-analysis who were taking statins for secondary prevention and looked at 5-year effectiveness, as shown in the table below.  Given the absolute risk reductions observed for hospitalizations for MI, revascularization, and strokes, the estimated number of hospital days avoided across all the patients was 0.33.   In contrast, the adherence study reported an average of 1.18 fewer hospital days for adherent patients versus non-adherent patients with dyslipidemia.

It is not plausible that the nearly 4-fold greater hospital reduction reported in the adherence study (1.18 versus 0.33 days) was due to greater medication compliance.  The implausibility is compounded by the fact that I included more severe patients, followed them for a much longer period of time, and examined the full effect of statins versus placebo rather than the effect of differences in adherence, all of which inflated our hospital days avoided.

Patients with Previous MI or CAD        
Event Statin No Statin Absolute Reduction Length of Stay Hospital days avoided
MI 12.00% 15.00% 3.00% 5 0.15
Revascularization 11.00% 13.70% 2.70% 5 0.14
Stroke 3.20% 4.00% 0.80% 5 0.04
        Total hospital days avoided 0.33

Plausibility tests are quick and powerful and can be used to test the ROI claims from disease management vendors, medication compliance programs, and many other healthcare services.  Recognizing the need for such tools and plan sponsors’ limited time to examine vendors’ savings claims, we designed plausibility calculators specific to disease management and value-based insurance to help plan sponsors discern fact from fiction.  They are free so the next time you are listening to a vendor’s sales pitch, you can do a quick reality check.

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  1. Value-Based Insurance Design: A Bargain at $10 Per Day? « Rx Outcomes Adviser

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