Abstract
INTRODUCTION: Screening for LTB is mandatory before starting therapy with Tumor Necrosis Factor (TNF) alpha inhibitors. Recently, a whole blood interferon gamma assay (QuantiFERON®) emerged as additional test for screening of LTB usually consisting of tuberculin skin test (TST) and chest X-ray. However, in patients with immunosuppression (IS) both tests might show limitations. AIMS & METHODS: We aimed to compare results from QuantiFERON®, TST and chest X-ray in consecutive IBD patients with or without IS with the indication of anti TNF alpha therapy. Signs indicative of LTB from chest x-ray included granuloma, bihilar lymphadenopathy and pleura scarring. TST was assessed positive if induration ≥5mm appeared after 48-72h of intracutan application of tuberculin /2 units in 0,1ml/ in immunosuppressed and ≥10mm in all other IBD patients. QuantiFERON® was positive if quantitative measurement indicated ≥ 0,35 U/ml. In pts under IS type, dose, and duration of therapy were obtained. RESULTS: In 145 patients all three tests for LTB were performed. QuantiFERON® test failed on samples from 15/145 (10.3%) patients, resulting in 130/145 (89.7%) patients on whom results from all 3 screening tests were available. There were 109 pts (75.2%) with and 36 (24.8%) without IS. Seventy-six patients (52.4%) were under maintenance AZA/6-MP, 49 (33.7%) under steroids ≥10mg daily for ≥ 2weeks and 16 subjects (11%) received infliximab within a median of 8 (6-16) weeks previously. The impact of IS therapy on TST and QuantiFERON® is shown in the table. The median TST induration was 2.11 mm (±5.2) for the entire study population, 2.07 mm (±5) in pts with and 2.22mm in pts without IS (±5.7) (p=0.882), respectively. Among subjects with positive TST median induration was 12.5 mm (±5.3) in IS patients (n=17) and 16mm (±2.4) in pts without IS (n=5, p=0.058). There was a higher rate of positive QuantiFERON® results in patients without IS (p=0.036). CONCLUSION: Our results reveal significant influence of IS on single TST and QuantiFERON® results in IBD patients undergoing screening for LTB and suggest an underestimation of the actual rate of LTB. Therefore, LTB screening might be best performed before IS treatment.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have