Background Patients treated with biologic agents have increased risk of developing active tuberculosis (TB). It is essential to screen patients for latent TB before starting a biologic drug. Population is vaccinated with BCG in Turkey and BCG vaccination decreases the specifity of tuberculin skin test. QuantiFERON-TB Gold In-Tube Assay (QFT) is an another good option to screen latent TB.
Objectives The objective of this study was to assess reliability of QFT test for latent TB before biological treatment.
Methods Hacettepe University Rheumatology Biologic Registry (HUR-BIO) is a single center biological registry since 2005. Between Nov 2011 and July 2015, 1347 patients were assessed by QFT for latent TB. All consecutive patients were evaluated by a standard questionnaire between July 2015 and October 2016. This questionnaire included demographic characteristics, medical and treatment history, symptoms of active TB. 671 patients were assessed by the physicians. TB status of other 676 patients were checked from Turkish national tuberculosis registery records. It's an obligatory disposition for physicians to inform health ministery about TB cases and all TB patients must be recorded in those regitry. The mean TB incidance per year was calculated for every anti-TNF agents and non-TNF biological agents.
Results Total 1347 (58.1% female) patients were recruited to study. Mean age was 42±12 years. Diagnosis were followed; RA 436 (32.4%), SpA 844 (62.5%), others 67 (5.1%). Total biological drug exposure was 2329 patient-years; adalimumab (660 years), etanercept (630 years), infliximab (426 years), golimumab (283 years), certolizumab (78 years), and total anti-TNF duration (2071 years). Non-TNFi exposure was 258 patient-years. Positive and indeterminate QFT results were found in 267 (19.8%) and 20 (1.5%) patients, respectively and those patients were prescribed INH prophylaxis. In addition, INH was prescribed to 37 (2.7%) patients according to chest X-Ray and physician decision. Pulmonary TB found in 3 of 1347 (0.22%) patients. TB was developed 38, 28 and 21 months after TNFi. The mean TB incidance per year was 128.8/100.000 for all biological drugs. The mean TB incidance per year according to QFT positive and negative patients were 181.8/100.000 vs 112.4/100.000.
Conclusions According to QFT screening for latent TB, INH was started almost 20% of patients. However, if we used TST for latent TB test in BCG vaccinated countries, INH would started almost 70–80% of patients. Therefore QFT was a good tool for latent TB screening in BCG vaccinated countries. Consequently, QFT test seems acceptable to determinate latent TB during biological drug usage. In addition, TB incidance has increased almost 7 times of our national TB incidance.
Disclosure of Interest None declared