Screening for latent tuberculosis infection in psoriasis and psoriatic arthritis patients in a tuberculosis-endemic country: a comparison of the QuantiFERON®-TB Gold In-Tube test and tuberculin skin test

Since the introduction of biologic therapies for tuberculosis (TB), screening for latent TB infection has increased in importance, especially in countries in which TB is endemic. The aim of this study was to evaluate the effect of psoriasis on tuberculin skin test (TST) results and to compare two TB screening tests, the TST and QuantiFERON (R)-TB Gold In-Tube (QFT-GIT) test, in psoriasis and psoriatic arthritis (PA) patients living in a TB-endemic country (Turkey). This prospective study included 61 psoriasis and 40 PA patients, and 58 healthy controls. Demographic data, medical history, human immunodeficiency virus (HIV) status, level of education, smoking status, exposure to TB, personal and family histories of TB, and bacillus Calmette-Guerin (BCG) vaccination status were recorded for all participants. The TST and QFT-GIT were performed in all participants. The mean +/- standard deviation TST indurations in the patient and control groups were 12.6 +/- 6.4 mm and 10.2 +/- 6.5 mm, respectively (P = 0.051). The TST positivity rate was higher in patients than in controls (86.1% vs. 37.9%; P < 0.001), whereas QFT-GIT positivity did not differ significantly (patients: 20.8%; controls: 17.2%; P = 0.737). False positive results can lead to unnecessary prophylactic TB treatment; therefore, the cut-off point for TST positivity in psoriasis and PA patients should be re-evaluated, or other tests, such as the QFT-GIT, should be used.