Our experiences with diagnosis of latent tuberculosis in patients before the initiation of anti-TNF treatment with QuantiFERON-TB Gold test

Abstract Objective Recently, the possibility of anti-TNF treatment was introduced into clinical praxis in Slovakia (2001 – Infliximab, 2003 – Etanercept and 2005 – Adalimumab). One of the most serious and redoubtable side effects of anti-TNF treatment is the development of latent tuberculosis (TBC). Subjects with latent TBC have positive skin tuberculin test and in their organisms, there are vital TBC bacteria which are inactive (“hibernating status”). After immunosuppression of various origins, it comes to the activation of these bacteria and these persons become contagious. Latent form of tuberculosis is curable. QuantiFERON-TB Gold Test presents the break in the diagnosis of latent tuberculosis on the basis of quantification of interferon-gamma produced by T-lymphocytes after stimulation with mycobacterial proteins. Since 1 st April 2007, this test was according to the Methodic Letter of Main expert for Pneumology and Phtiseology in Slovakia incorporated into the standard algorithms for screening of latent TBC before the initiation of anti-TNF treatment. Aim Examination of the patients with QuantiFERON-TB Gold Test before the initiation or in continuance of anti-TNF treatment. Methods We enrolled all the 106 patients before the initiation of anti-TNF treatment (indicated after 1 st April 2007) and 73 other patients with already initiated anti-TNF treatment. Nowadays there are approximately 500 patients with rheumatoid arthritis, psoriatic arthritis and ancylosing spondylitis treated with anti-TNF medication. Results In patients with planned anti-TNF treatment (all from 1 st April 2007) we observed in 70% negative, 9% positive and 6% questionable results. In 15% we are still waiting for the final result of the test. In the group of patients with already initiated anti-TNF treatment we noted in 93% negative, 4% positive (3 subjects) and 3% questionable results. In the patients we verified reactivation of the latent tuberculosis during anti-TNF treatment. Conclusion All the patients with negative test results initiated anti-TNF therapy. Those with positive results were firstly treated according to the protocol for the prophylactic anti-tuberculosis therapy during 6 months and after 2 months of therapy after consensus with pneumologist-phtiseologist we could start anti-TNF therapy. Patients with questionable test results (immunosuppressed) underwent after one month re-testing. Surprisingly, we found the lower frequency of questionable results in the group of already treated patients (3%) in comparison with those with planned anti-TNF treatment (6%). Test is suitable for the identification of highly risk persons, for the detection of hidden form of tuberculosis, decreased the risk of false negative results and prevents the development of active diseases. It allows to eliminate the mistakes in the interpretation of skin tuberculin test, economically execute desired number of the samples, accelerate the establishment of the diagnosis and consecutively specifically initiate adequate therapy. It is necessary to consider also the risk of false positive results of this test.