Screening for TB in Hospitalised Patients with Inflammatory Bowel Disease before Anti-TNF Therapy: Is QuantiFERON(R) Gold Testing Useful?

Background-Tumour necrosis factor alpha (TNF alpha) plays an important role in the pathogenesis of inflammatory bowel disease (IBD) and in immunity to Mycobacterium tuberculosis. Patients should be tested for latent tuberculosis infection using interferon-gamma release assays (IGRA/QF) prior to anti-TNF alpha therapy. Indeterminate QF results can delay anti-TNF alpha therapy. We sought to investigate factors associated with indeterminate QF results. Method-Retrospective study of all IGRA tests requested for gastroenterology patients in 2017. We compared inpatients and outpatients and investigated factors potentially associated with QF usefulness (steroid exposure, C-reactive protein (CRP), hypoalbuminaemia, thrombophilia). Results-We included 286 outpatients and 74 inpatients with IBD. Significantly more inpatients had an indeterminate IGRA (52.7% vs. 3.14% in outpatients; p < 0.0001). Laboratory parameters reflecting inflammation (high CRP, low albumin, low haemoglobin and high platelets) were also associated with an indeterminate QF (p < 0.0001). Exposure to steroids was more common in patients with an indeterminate QF (p < 0.0001). A binary logistic regression analysis revealed inpatient status and steroid exposure to be independently predictive of an indeterminate QF (p < 0.0001). Conclusion-There is a high chance of indeterminate QF results in inpatients. QF testing should ideally be performed in the outpatient setting at diagnosis.