Background The evolution of Tumor Necrosing Factor inhibitor (TNFi) in the treatment and management of chronic inflammatory disease has revolutionised patients' disease and improved their quality of life substantially. However evidence shows there is an increased risk of infection, in particular mycobacterium infection and reactivation of a latent TB infection (LTBi)1, in patients receiving TNFi treatment. The screening of patients for LTBI is mandatory before initiating TNFi therapy; although TST is widely used in the diagnosis of LTBI, there is a lack of sensitivity and specificity2.
Despite our initial TB screening policy, which included risk history assessment, chest X-ray (CXR), and TST, approximately 1% of patients over a 10 year period who screened negative subsequently developed active TB, frequently extra-pulmonary and treatment-resistant3. Data from our previous study revealed Quantiferon testing may identify additional patients with latent TB in Mantoux negative patients, indicating a potential benefit for Quantiferon testing as part of TB screening4.
Objectives In this study, we sought to evaluate performance and benefits of incorporating Quantiferon in a TB screening protocol in our Rheumatology centre.
Methods 109 patients were screened for LTBi. Their diagnoses including rheumatoid arthritis, psoriasic arthritis, ankylosing spondylitis, inflammatory arthritis and all patients were screened over a twelve month period (December 2011-December 2012). In the modified screening protocol, TST was replaced with Quantiferon blood test; however risk history assessment and CXR remain part of the screening protocol. Quantiferon positive patients were treated with isoniazid for LTBi.
Results Mean age 50.5 years, 55% female. Diagnosis: 50.5%, 27% and 21% had RA, PsA and AS, respectively, 8% (9 patients) had positive Quantiferon, all received LTBi chemoprophylaxis. CXR suggestive of LTBi in 2.8% (3), all subsequently had normal CT- thorax. These 2.8% (3) had negative Quantiferon testing. 7% (8) had high TB risk history, only one patient tested Quantiferon positive. To date, no patient from this cohort has developed active TB after a mean follow-up of two years.
Conclusions Replacing Mantoux testing with Quantiferon has proven a safe and effective strategy for LTBi screening. Quantiferon testing helpes improve TB testing compliance and eliminates false – positive results associated with BCG5. Quantiferon testing requires one clinic visit with substantial benefits for the patient and the rheumatology nurse specialist identified in terms of time and indirect costs. Mantoux testing can be inconvenient as it requires two patient visits.
Kane J. TNF blocking agents and tuberculosis; new drugs illustrate an old topic. Rheumatology (Oxford) 2005; 44, (10), 1205-1206.
American Thoracic Society.Targeted tuberculin testing and treatment for latent tuberculosis infection.Am J Respir Crit Care Med 2000;161:221S-47S.
Mongey A-B et al. Late Onset Tuberculosis Infection in Patients Receiving Anti-TNFα Therapy. QJM (in press).
O'Flynn E. et aI. Quantiferon testing in mantoux neg. patients commencing TNFi therapy identifies additional at risk patients. I.S.R Annual General Meeting Oral Presentation, September 2011 (Ref 11A036).
Chiu H-Y et al. Brit J Derm 2011; 164,553-559.
Disclosure of Interest : None declared