Screening for tuberculosis infection prior to initiation of anti-TNF therapy

Abstract

T-cell interferon-gamma release assays (IGRAs) are more specific and probably more sensitive than the tuberculin skin test (TST) for the diagnosis of latent tuberculosis infection (LTBI). Patients with immune-mediated inflammatory diseases (IMID) and suspected LTBI who are candidates for anti-TNF therapy are at a significant risk of TB reactivation yet are prone to false-negative TST results because they are already on immunosuppressive medications. The role of these new blood tests in this patient population is therefore of considerable interest but is currently unclear. The limited published evidence-base shows that agreement between IGRA and TST results is poor in patients with IMID compared to patients without IMID, due to lower proportions of TST-positive results in patients with IMID. Discordant TST-positive, IGRA-negative results are associated with prior BCG vaccination and discordant TST-negative, IGRA-positive results are associated with steroid therapy. Notably, positive IGRA results are more closely associated with the presence of risk factors for LTBI than TST. The percentage of indeterminate IGRAs can be up to 12%. IGRA results in patients already taking anti-TNF agents currently remain uninterpretable. Given the clinical imperative to prevent reactivation of TB in patients starting anti-TNF therapy, screening algorithms should maximise diagnostic sensitivity for detection of LTBI. Therefore, a positive result to either an IGRA or TST, in addition to currently recommended clinical screening for risk factors for LTBI, should prompt consideration of preventive treatment of LTBI in this population.

Diagnosis of tuberculosis infection using interferon-γ-based assays

“…29,31 Experience with the IFN-γ-based tests in this population, although promising, is still limited. 32,33 Overall, agreement with the TST seems to be poor. [34][35][36] The discordant positive TST and negative IFN-γ-based test results have been attributed to false-positive TST results, 37,38 whereas the discordant negative TST and positive IFN-γ-based test results have been considered false-negative TST results due to the immunosuppressive therapy being taken by these patients.…”

Use of adenosine deaminase measurements and QuantiFERON in the rapid diagnosis of tuberculous peritonitis

“…The second-generation assay QuantiFERON-TB Gold (QFT-G) also measures the release of IFN-c after in vitro stimulation of samples with specific region of difference 1 (RD1) antigens from M. tuberculosis: early secretory antigenic target-6 (ESAT-6) and culture filtrate protein-10 (CFP-10). The QuantiFERON-TB Gold in-tube assay is a new-generation test that includes an additional M. tuberculosis antigen, TB7.7, encoded by a phage-inserted region, RD11 (Lalvani & Millington, 2008). All of the antigens used in the QFT tests are present in the M. tuberculosis complex but not in the vaccine against TB or in any of the non-TB mycobacteria, except Mycobacterium kansasii, Mycobacterium marinum and Mycobacterium szulgai; therefore, the QFT assays can be used to discriminate between persons infected with M. tuberculosis and persons vaccinated against TB or exposed to non-TB mycobacteria (Andersen et al, 2000).…”

Tuberculose pleural após uso de adalimumabe na doença de Crohn: relato de caso

“…Para tentar melhorar a acurácia dos testes cutâneos, novas técnicas vêm sendo testadas ainda em caráter experimental 6,11,[13][14][15] .…”