Objective: The aim of this study was to determine the occurrence of latent TB infections (LTBI) and active Tuberculosis (TB) in a cohort of inflammatory bowel disease (IBD) patients treated with biologics. We also examined the effects of immunosuppressive drugs on indeterminate interferon-gamma release assays (IGRA) in LTBI screening. Design: Retrospective study of patients treated with biologics between March 2007 and November 2015. Setting: St Mark’s Hospital, North West London, UK. Patients: 732 patients with IBD who were screened for LTBI using either TST or IGRA before starting a biological treatment. Methods: Retrospective case note review of all IBD patients who were screened for LTBI prior to initiating biologics. Patients who developed active TB were identified from the London TB register. Results: Of 732 IBD patients, 31 (4.2%) were diagnosed with and treated for LTBI with no significant side effects. Six of 596 patients (1.0%) who received biologic treatment developed active TB. There was a higher proportion of indeterminate IGRA in the immunosuppressive medication group compared to the non-immunosuppressive group (33% (59/181) compared to 9% (6/66), p<0.001). The combination of steroids and thiopurines had the highest proportion of indeterminate IGRA (64%, 16/25). High and low doses of steroids were equally likely to result in an indeterminate IGRA result (67% (8/12) and 57% (4/7), respectively). Conclusions: This study highlights the challenges of LTBI screening prior to commencing biologic therapy, and demonstrates the risk of TB in patients who have been screened and who are receiving prolonged and continuing doses of anti-TNF.