A Prospective Cohort Study Comparing the Performance of Interferon Gamma Release Assays in Autoimmune Skin Diseases.

To the Editor: Autoimmune disease patients are more likely to reactivate latent tuberculosis (TB) than the general population, and the risk increases in immunosuppressed patients.1 TB screening is recommended prior to immunosuppressive therapy or clinical trial enrollment.2,3 Two interferon gamma release assays (IGRAs), QuantiFERON-TB Gold Plus (QFT-Plus; Qiagen) and T-SPOT.TB test (Oxford Immunotec), demonstrate similar sensitivity and specificity in healthy populations.4 However, immunosuppressed patients are more likely to have an indeterminate or invalid IGRA due to an inadequate immune response.