Abstract
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.
- © 2011 ERS
