Patch testing is the best diagnostic test for allergic contact dermatitis. However, there is presently a lack of data on the test's geographic availability and the characteristics of the providers offering this test across the United States.

To evaluate the geographic variation in the availability of patch testing for the Medicare population and to characterize the temporal trends of patch testing cost, use, and provider specialty from 2012 to 2017.

Retrospective cohort study of the Medicare Provider Utilization and Payment Data from 2012 to 2017.

As of 2017, patch testing was available in 20.3% of metropolitan counties and in 1.1% of nonmetropolitan counties. From 2012 to 2017 in metropolitan regions, the number of beneficiaries tested by dermatologists grew by an average annual growth rate of 1.84%, whereas those tested by allergists grew by an average annual growth rate of 20.31%. Most providers that averaged use of 80 or more patches per beneficiary were dermatologists (76.3%).

Analysis was restricted to Medicare Part B claims; data were unavailable on individuals with commercial insurance.

Most of the increase in patch testing utilization from 2012 to 2017 has been in metropolitan regions. Although growth was especially prominent among allergists in metropolitan counties, the majority of providers performing comprehensive patch testing were dermatologists.