Variations of tuberculin skin test in patients with rheumatologic disorders and under anti-TNF treatment

Abstract

Aim: Nowadays PPD is the most inexpensive and easy to apply modality of test in identification of latent tuberculosis infection. Isoniazid (INH) prophylaxis must be given before usage of anti-TNF-α agents for patients. We aimed to investigate the change in Tuberculin skin test (TST) levels and Isoniazid (INH) prophylaxis rates in patients with inflammatory rheumatic diseases treated with anti-tumor necrosis factor alpha (TNF-α) agents. Methods: A cross-sectional study was planned. Patients with inflammatory rheumatic diseases treated with anti-TNF agents were included in the study. Demographic data, initial TST level and INH prophylaxis had obtained from patient’s files. Control TST tests had done at tuberculosis dispensaries in different time periods such as 1-2 / 2-3 / 3-4 / ≥4 years of anti TNF treatment. INH prophylaxis rates according to initial and control TST tests were compared. The relationship between INH prophylaxis and duration of anti-TNF therapy were examined.Results: A total of 117 patients were included in the study. The mean age of the patients (81 male, 36 female) was 40.4±12.90. The control TST levels was significantly higher than initial TST (p=0.001). INH prophylaxis was given to total 99 (84.6%) of 117 patients (to 63 (53.8%) according to initial and to 36 (30.8%) according to control TST tests). There was no relationship between duration of anti TNF therapy and INH prophylaxis initiation (p=0.180). Conclusion: Anti-TNF treatments may reduce the rates of false-negative TST in patients with rheumatic diseases and latent tuberculosis (LTBI) at any stage of the treatment. Therefore, LTBI, which is not determined with initial TST tests, may be determined with TST test applied in the later stages of anti-TNF treatment, and the risk of active tuberculosis can be reduced by INH prophylaxis in this patients.