GEOGRAPHIC VARIATION IN RESPONSE TO FDA WARNINGS: EVIDENCE FROM A NATIONALLY INTEGRATED SYSTEM

Purpose: Previous research has shown that clinician response to FDA warnings may not be adequate, which could impact patient health negatively. Further, there may be variation in how clinicians respond to FDA warnings, which may lead to inconsistency in patient treatment and insufficient patient protection. While geographic variation in various aspects of healthcare in the United States has been documented widely, there is limited literature that documents geographic variation in response to FDA warnings. Understanding this variation is critical to policymakers and hospital administrators responsible for communicating FDA warnings and setting guidelines for its providers, particularly for large national healthcare systems, whose actions may be guided by the nature and extent of the observed variation.

Methods: We use a landmark FDA black box warning on a glucose lowering drug rosiglitazone to study geographic variation. Using a national cohort of 550,959 diabetes patients from the Department of Veterans Affairs (VA), we analyze variation in rosiglitazone use from 2003-2008, aggregated on a quarterly basis, for each of the 21 geographical regions in VA called the Veterans Integrated Service Networks (VISNs), a set of regional service networks that provide integrated care to veterans based on geographic location. We use multivariate logistic regression to estimate the effect of each VISN on the likelihood of a patient receiving a rosiglitazone prescription.

Results: At the aggregate VA level, rosiglitazone use decreased substantially after the FDA warnings. There was substantial geographical variation in rosiglitazone use before FDA warnings were issued, but this variation increased considerably afterwards. The variation factor rose from an average of 2.8 in the pre-warning periods to an average of 3.9 in the post-warning periods. The VISN in which the patient's primary care facility is located, significantly and differentially, affected the odds of a patient being prescribed rosiglitazone, after controlling for various patient and facility-level factors. Further, there are geographical differences in the timing of when rosiglitazone use reached its peak usage level in each VISN. Twelve out of 21 VISNs achieved their peak level before FDA warnings were issued.

Conclusion: Hospital administrators and policymakers need to eliminate barriers and develop effective mechanisms for disseminating information related to FDA warnings and setting up guidelines for its providers in order to reduce the variation.