Background: Anti-TNF therapy is increasingly used in chronic inflammatory diseases. As it is related to increased risk of tuberculosis (TB), screening is mandatory before starting on anti-TNF. Negative predictive value (NPV) of tuberculin skin test (TST) and interferon gamma assay (IGRA) are still not well defined in these patients. Aim: Determination of TST and IGRA NPV for progression to disease in patients on anti-TNF therapy. Methods: Retrospective analysis of anti-TNF candidates screened for TB between Jan-2008 and Jun-2010. Screening included symptom inquiry, chest radiograph, TST and IGRA. After active TB exclusion, all who tested positive TST or IGRA or had radiological evidence of past non-treated TB or recent contact with TB started preventive therapy (PT). Follow-up maintained until Jan-2011. Evaluation of NPV on patients who did not start PT. Results: We evaluated 158 patients. Mean age: 42.8±12,6 years; 81 males. Most frequent co-morbidities: psoriasis (34%), inflammatory bowel diseases (26%) and rheumatoid arthritis (16,4%). At screening 85 patients (53,8%) were on immunosuppressant drugs,mostly steroids; 8 were on anti-TNF. None of the patients who started PT developed active TB. Forty-five immunocompetent and 24 immunocompromised patients negative for TST and IGRA did not do PT and started anti-TNF. One immunocompromised patients developed active TB, 22 months after etanercept initiation. A NPV for progression to disease (for TST and IGRA) of 95,8% in immunocompromised, and 100% in immunocompetent patients was defined. Discussion: NPV of available TB screening tests is higher in immunocompetents. TB screening should be advised in an early stage of disease before starting any immunosuppressant drugs.
Campainha et al. (Thu,) studied this question.