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Quantiferon TB gold test: The new standard for screening of latent tuberculosis in patients with rheumatoid arthritis?
  1. Petros Efthimiou (efthimpv{at}
  1. New Jersey Medical School, UMDNJ, United States
    1. Sunita Sood (soodsu{at}
    1. New Jersey Medical School, UMDNJ, United States


      We read with interest the report by Ponce de Leon et al.1, where the authors argued that tuberculin skin testing (TST) may not be an optimal test for the diagnosis of latent tuberculosis infection (LTBI) in patient with rheumatoid arthritis (RA). We would like to contribute to these findings, based on our clinical experience with a new screening tool called the QuantiFERON TB-Gold (QFT-G) test. While screening policies vary significantly between countries, it is generally recommended that all patients with RA should undergo screening for M. Tuberculosis latent infection prior to the initiation of treatment with biologic agents, especially the tumor necrosis factor (TNF) α inhibitors.2 Patients with RA may not be able to produce an adequate delayed type hypersensitivity (DTH) reaction to tuberculin because of their deficient cell mediated immunity.3-5 QFT-G is a whole blood, antigen-specific, test that utilizes synthetic peptides representing two M. tuberculosis proteins, ESAT-6 and CFP-10. After incubation for 16 to 24 hours, the amount of interferon (IFN)-γ secreted by monocytes in response to these antigens is measured.7 8 T-SPOT.TB, not yet available in the US, is another antigen-specific blood test utilizing the enzyme-linked immunospot (ELISPOT) assay technique. These new tests may be applicable to patients with RA, where false negative TST can have adverse consequences in patients treated with TNF inhibitors. We have identified two patients in our rheumatology clinic that were TST negative but were subsequently diagnosed with LTBI by the QFT-G test. Patient 1 is a 73 year-old black female who presented with symmetric bilateral synovitis of the metacarpophalangeal joints, was seropositive for rheumatoid factor (RF) and antinuclear (ANA) antibodies, with radiographic evidence of inflammatory erosive arthropathy. She was diagnosed with RA and had a negative TST. She was an incomplete responder to methotrexate and corticosteroids and the decision was made to initiate anti-TNF treatment. Repeat TST was again negative 2 months after the first testing. However, she tested positive for QTB-G and is currently completing a 9-month isoniazid/vitB6 course for LTBI. A confirmatory chest radiography showed apical pleural thickening and upper lobe fibrosis, consistent with previous history of primary tuberculosis. Patient 2 is a 61 year-old black male with severe erosive RA, who screened negative by TST prior to immunosuppressive treatment. A pre-operative chest radiograph showed mild interstitial scarring, without any pleural pathology. He partially responded to methotrexate and became a candidate for anti-TNF treatment. Positive QTB-G testing prompted the initiation of a 9-month isoniazid/vitB6 course. In summary, QTB-G may be a more sensitive screening tool for LTBI in RA patients with impaired DTH response to tuberculin. Additional benefits include: it requires a single patient visit to draw the blood sample, results can be available within 24 hours, it is not subject to reader bias, and, most importantly, is not affected by prior BCG (bacille Calmette-Guérin) vaccination.8 However, the test is not widely available yet and careful studies comparing it to the TST are needed to validate our findings in the RA population.

      • QuantiFERON TB-Gold test
      • TNF-inhibitors
      • latent tuberculosis
      • rheumatoid arthritis
      • tuberculin skin test

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