Vol.20 No.1

Original Article

Usefulness and limitations of QuantiFERON-TB Gold in Japanese rheumatoid arthritis patients: proposal to decrease the lower cutoff level for assessing latent tuberculosis infection

Authors

Tomoyo Maeda1 , Shogo Banno1,3 , Shinji Maeda1 , Taio Naniwa1 , Yoshihito Hayami1 , Maiko Watanabe1 , Rei Itoh1 , Shigeki Sato2 , Ryuzo Ueda1

  • Division of Rheumatology, Department of Medical Oncology and Immunology, Nagoya City University Graduate School of Medical Science, Nagoya, Aichi, Japan
  • Division of Respiratory Diseases, Department of Medical Oncology and Immunology, Nagoya City University Graduate School of Medical Science, Nagoya, Aichi, Japan
  • Division of Rheumatology, Department of Medical Oncology and Immunology, Nagoya City University Hospital, Kawasumi, Mizuho-ku, Nagoya Aichi, 467-8601, Japan
Received:

2 June 2009

Accepted:

19 August 2009

Published online:

25 September 2009

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Abstract

We aimed to determine the sensitivity and specificity of QuantiFERON-TB Gold (QFT-G) in Japanese rheumatoid arthritis (RA) patients with a past history of tuberculosis (TB). We assessed whether it is possible to decrease the cutoff using receiver operating characteristic (ROC) analysis. We evaluated chest computed tomography (CT) findings, prior history of treatment, and contact with active TB in 370 RA patients. Forty-nine patients before initiation of treatment with tumor necrosis factor (TNF) inhibitors were divided into two groups: 22 with a past history of TB and 27 without. We estimated the efficacy of QFT-G compared with the tuberculin skin test and antituberculosis (anti-TB) glycolipid antigen antibody. QFT-G was positive (≥0.35 IU/ml) in 13.6% with a past history of TB, increasing to 27.3% at the intermediate range cutoff of 0.1 IU/ml. The sensitivity and specificity of QFT-G was 0.27 and 1.00, respectively, at 0.1 IU/ml. Using ROC analysis, the area under the curve (AUC) of QFT-G but not for the other two tests was significantly large. QFT-G is a useful diagnostic method due to its superior specificity, but the use of a cutoff value of 0.35 IU/ml will likely result in an underestimate. We propose that a lower interferon-γ (IFN-γ) titer of 0.1 IU/ml be adopted when deciding to administer anti-TB drugs before initiation of TNF inhibitors.

Key words

Tuberculosis - Rheumatoid arthritis - Latent tuberculosis infection - Interferon-γ release assay - Tuberculin skin test