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Volume 42, Number 3, June 2009

Comparison of 2 interferon-γ assays and Roche Cobas Amplicor Mycobacterium tuberculosis assay for rapid diagnosis of tuberculosis among patients with suspected tuberculosis in Taiwan


Chien-Hong Chou, Hsiao-Leng Hsu, Li-Na Lee, Po-Ren Hsueh, Kwen-Tay Luh
Department of Internal Medicine, National Taiwan University Hospital Yun-Lin Branch, Yun-Lin; Department of Laboratory Medicine; and Department of Internal Medicine, National Taiwan University College of Medicine and Hospital, Taipei, Taiwan

Received: November 29, 2008       Accepted: December 5, 2008   

 

Corresponding author:

Dr. Po-Ren Hsueh, Department of Laboratory Medicine, National Taiwan University Hospital, No. 7, Chun Shan South Road, Taipei 100, Taiwan. E-mail: Dr. Po-Ren Hsueh

 



 

Background and purpose: 

Two commercial interferon-γ (IFN-γ) assays, which are commonly used for diagnosing latent tuberculosis (TB), are also useful for diagnosis of active TB. In this study, the IFN-γ assays and polymerase chain reaction (PCR) for diagnosis of TB were compared.
 



 

Methods:

 A prospective comparison of the performance of 2 commercial IFN-γ assays — QuantiFERON®- TB Gold (QFT-G) and T-SPOT®.TB (T SPOT) — and PCR using the Roche Cobas Amplicor Mycobacterium tuberculosis (RCA-TB) assay for the rapid diagnosis of TB was conducted from January 2007 to December 2007 at a university-affiliated hospital in Taiwan.

 



 

Results:

Of 187 patients enrolled in the study, results from both T SPOT and QFT-G were available for 154, including 109 patients with active TB and 45 with no TB. The sensitivity of T SPOT (89.0%) was higher than that of QFT-G (71.4%). RCA-TB had the highest sensitivity (90.2%) and specificity (100%), but was usually performed in patients with positive acid-fast bacilli smear test. In patients with extrapulmonary TB, T SPOT had a high diagnostic value (sensitivity, 81.3%). A significant discordance between the 2 IFN-γ assays was also noted. IFN-γ assays provided a more rapid diagnosis for tuberculosis than the conventional culture method (mean ± standard deviation, 8.23 ± 12.86 days; p < 0.001).
 



 

Conclusion:

Use of IFN-γ may shorten the time to diagnosis of TB, especially for smear-negative patients and those with extrapulmonary disease.



 

Key words:

Interferon-gamma; Tuberculosis

 



 

J Microbiol Immunol Infect. 2009;42:251-257.