The Performance of Quantiferon TB Gold In-Tube as a Screening Tool in Paediatric Rheumatology prior to Initiation of Infliximab: A Single Centre's Experience

Background. Patients with autoimmune diseases and latent tuberculosis infection (LTBI) are at risk of developing catastrophic tuberculosis disease following infliximab treatment. Quantiferon-TB gold in-Tube (QTB) has proven a more accurate screening tool than tuberculin skin test (TST) in adult populations. Objectives. To assess the utility and validity of QTB in children, prior to treatment with infliximab. Methods. Retrospective cohort of patients started on infliximab following endorsement of QTB as a screening tool by the NICE guidelines in 2006. Results. Twenty three patients (12 females and 11 males) were included in the study. A chest radiograph (CXR) and QTB was performed prior to starting infliximab. Fourteen patients had a recorded negative TST result. One patient had a positive QTB while two had indeterminate results. Their CXRs were not suggestive of TB and TSTs were negative. The patients with indeterminate results were started on infliximab and had regular clinical assessment for TB disease. Repeat QTB was negative in one while remained indeterminate in the other. None of our 23 patients developed TB. Conclusion. QTB is a useful screen tool for LTBI. Indeterminate results warrant careful assessment and re-evaluation, but should not preclude from initiation of anti TNF treatment. 1. Background Antitumor Necrosis Factor alpha (TNFα) agents are a rapidly developing field of medicines in pediatric rheumatology. Recent papers have presented the efficacy and effectiveness of anti-TNFα therapy in disease control and improvement in quality of life. Agents commonly used include infliximab, an anti-TNFα chimeric monoclonal antibody, etanercept, an anti-TNFα receptor fusion IgG protein, and adalimumab, a humanized monoclonal antibody acting as TNFα receptor blocker. However, initiation of anti-TNFα treatment is not without risk. TNF is released by macrophages and is a potent regulator for granuloma formation and limitation of the mycobacterium tuberculosis (TB) infection. Anti-TNFα medications suppress TNF actions and inhibit its restrictive role in controlling TB, thus potentially leading to reactivation of TB disease in those with LTBI. This may have catastrophic consequences especially in patients with an already dysregulated and compromised immune system [1]. A tool that could rule out TB infection prior to anti-TNFα medications is therefore highly desirable. Over the last three years the use of Interferon gamma releasing assays (IGRAs) has been increasingly introduced in order to verify or rule out latent TB infection (LTBI) [2]. There are