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Clinical utility of a T cell‐based assay in the diagnosis of extrapulmonary tuberculosis

2008; Wiley; Volume: 14; Issue: 2 Linguagem: Inglês

10.1111/j.1440-1843.2008.01443.x

1440-1843

Yoshihiro Kobashi, Keiji Mouri, Shinichi Yagi, Yasushi Obase, Naoyuki Miyashita, Mikio Oka,

Mycobacterium research and diagnosis

ABSTRACT Background and objective: The aim of this study was to evaluate the QuantiFERON TB‐2G (QFT‐2G) results in patients with active extrapulmonary tuberculosis (E‐TB) to determine whether QFT‐2G test might be a reliable diagnostic method for detecting active E‐TB infection compared with the tuberculin skin test (TST). Methods: TST and QFT‐2G tests were performed for 35 patients with confirmed E‐TB, 30 with probable E‐TB and 45 who did not have E‐TB. Results: For patients with confirmed E‐TB, the positive rate of the TST was 57% and that of the QFT‐2G test was 86%. For patients with probable E‐TB, the positive rate of the TST was 60%, whereas that of the QFT‐2G test was 80%. However, the positive rate of the TST was 51% and that of QFT‐2G test was 9% for patients that did not have E‐TB. The QFT‐2G test showed a significantly lower percentage of false‐negative results compared with the TST. The sensitivity and specificity of the TST for the diagnosis of active E‐TB were 57% and 49%, respectively. By comparison, the sensitivity and specificity of the QFT‐2G test were 86% and 84%, respectively. When the results of the TST and QFT‐2G tests were separated by the site of E‐TB, the positive rates for both tests in patients with miliary tuberculosis were lower than those in patients with other E‐TB disease, although the difference was not significant. Conclusions: The QFT‐2G appears to be a reliable diagnostic test and in the appropriate clinical context QFT‐2G may be more useful than the TST to support a diagnosis of E‐TB. Studies are needed to evaluate its value also in situations of low clinical probability.