Changing the way we diagnose tuberculids with interferon gamma release assays.

Diagnosing tuberculids traditionally requires clinicopathological correlation together with positive tuberculin skin tests (TST) or demonstration of Mycobacterium tuberculosis (MTB) DNA by polymerase chain reaction (PCR). Interferon gamma release assays (IGRA) are new laboratory tests approved for the diagnosis of MTB infection. We describe three patients with tuberculids who had no other clinical feature of tuberculosis (TB) infection and negative PCR of skin biopsies. Their diagnoses were aided by positive IGRA.