Yield and cost effectiveness of mycobacterial infection detection using a simple IGRA-based protocol in UK subjects with inflammatory bowel disease suitable for anti-TNFα therapy

Abstract

Background and aimsTesting for LTBI is recommended prior to anti-TNFα agents. This includes an assessment of TB risk factors, chest radiograph, and interferon-gamma release assay alone or with concurrent Tuberculin skin testing. Here we review our experience and cost-effectiveness of using T-SPOT.TB IGRA to detect mycobacterial infection in patients with IBD suitable for anti-TNFα therapy. MethodsThis was a single-centre, retrospective review and economic evaluation (compared to British Thoracic Society guidance) of 125 adult IBD patients (90 anti-TNFα naïve, 35 established on anti-TNFα) tested for LTBI using T-SPOT.TB IGRA. ResultsAll subjects had normal chest radiographs and no clinical evidence for TB. 109 (87%) were BCG vaccinated. 27 (22%) of all patients tested were not using immunomodulation at the time of testing. 66 (53%) were taking thiopurines, 22 (18%)corticosteroids, and 35 (28%) anti-TNFα agents. One hundred twenty two (98%) had a negative IGRA result, two (2%) had positive results, and one (1%) had an indeterminate IGRA. A strategy using IGRA to guide TB preventative treatment produced cost savings of £10.79 per person compared to the BTS guidance. Eighty eight percent of the anti-TNFα naïve group have subsequently received treatment with either infliximab or adalimumab (median follow-up of 24months, IQR 18–30) with no cases of TB disease occurring. ConclusionsThe use of a simple screening protocol for LTBI incorporating T-SPOT.TB IGRA in place of TST in a largely BCG vaccinated population, many using immunomodulatory agents, appears to work well and is a cost-effective strategy in our IBD service.