Prevention of Tuberculosis in Patients Treated With Biological Therapies: Twenty Years’ Experience in a Specialised Tuberculosis Clinic in a Low-prevalence Country

This study builds on previous evidence to assess the risk of tuberculosis (TB) in patients treated with biologic therapies (BioT), the role of the interferon-γ-release assay (IGRA) QuantiFERON-TB (QFT) Gold as a stand-alone screening test, and whether periodic re-testing is warranted for patients with a negative pre-BioT screening. A total of 1,368 patients starting BioT were screened for TB infection using four screening strategies over four consecutive periods: (1) two-step tuberculin skin test (TST); (2) two-step TST plus QFT Gold In-Tube; (3) single-step TST plus QFT Gold In-Tube; and (4) QFT Gold In-Tube (or QFT Gold Plus) alone. All patients with TB infection were offered preventive therapy. TB infection was diagnosed in 327 (23.9%) patients (40.8%, 39.5%, 25.3%, and 14.8% in the first, second, third and fourth periods, respectively; P = .000). The adjusted odds ratios (ORs) with respect to the first period were 0.89 (95%CI, 0.55-1.44), 0.49 (95%CI, 0.33-0.73), and 0.23 (95%CI, 0.15-0.36) for the second, third and fourth periods, respectively. During follow-up, 11 patients (0.8%) developed TB. The probability of remaining TB-free after 11 years of BioT exposure was 99.1%, with no significant differences between screening periods (P = .372). All TB cases in patients with negative baseline screening occurred within the first year of BioT exposure, which would make systematic re-screening pointless. Although BioT-associated TB can be significantly reduced, it is not completely preventable. Neither dual testing nor periodic systematic re-screening for TB infection is warranted after a negative pre-BioT test.