A comparative analysis of tuberculosis in vitro screening in pemphigus patients selected for treatment with rituximab

Introduction
Patients qualified for the Polish government programme of treating severe pemphigus diseases with rituximab (RTX) available in 2018-2019 had to meet numerous criteria, including no active infectious disease. Aim: The clinical usefulness of tuberculosis screening with the QuantiFERON-TB Gold Plus (QFT-Plus) in native pemphigus patients selected for RTX treatment was statistically evaluated.

Material and methods
Eighteen pemphigus patients were examined with QFT-Plus prior to the intended RTX therapy. Ninety hospital employees examined with QFT-Plus due to contact with a cleaning worker who was diagnosed with active pulmonary tuberculosis were the control group.

Results
Six of 18 pemphigus patients had a positive QFT-Plus test result, one indefinite result and one initially indefinite and then negative. In the control group, 26 of 90 employees had a positive test result and none had an indefinite result. Statistical analysis by Fisher’s exact test showed no statistically significant difference in QFT-Plus positive results between the groups (p = 0.5577). Only in 1 patient with recurrent mucocutaneous pemphigus vulgaris previously treated with traditional immunosuppression, lung changes were detected by computed tomography. No employee had any changes in the chest radiograph.

Conclusions
Prior immunosuppression and autoimmunity might be the cause of indefinite test results, but they do not seem to increase positive results. In the native population, the QFT-Plus screening reveals a significant population exposure to M. tuberculosis infection independent of pemphigus autoimmunity, and such screening can be a starting point for identifying patients requiring anti-tuberculosis drug prophylaxis before combined RTX-glucocorticosteroid treatment.