Abstract
BackgroundInterferon-release assays (IGRAs) for diagnosing active pulmonary tuberculosis (PTB) are not yet fully validated, particularly in high TB-endemic areas as the People's Republic of China (PRC). The aim of this report was to assess the performance of the QuantiFERON-TB Gold In-tube (QFT-GIT) and tuberculin skin test (TST), in addition to microbiological results, as contributors for diagnosing active PTB in the PRC.Methods/Principal FindingsA total of 300 PTB patients, 41 disease controls (DC) and 59 healthy community controls (HCC) were included prospectively between May 2010 and April 2011 from two provinces of the PRC (Heilongjiang and Zhejiang). The QFT-GIT and TST yielded an overall sensitivity for active TB of 80.9% and 86.2%, and a specificity of 36.6% and 26.8%, respectively. The province of origin and smear microscopy status did not significantly impact the diagnostic values for PTB. However, using the TST with a 10 mm cut-off point, a significantly higher proportion of LTBI was observed in the DC than the HCC (p=0.01). Discordant results between the QFT-GIT and TST were found among 1/3 of the PTB, HCC and DC. Two-thirds of the individuals presented TST-positive/QFT-GIT-negative discordant results. The TST-negative/QFT-GIT-positive result was not associated with age or bacillary load. Cumulative QFT-GIT and TST positive results increased the overall sensitivity (95.9%), but it was associated with a dramatic decrease of the overall specificity (24.8%) leading to a suboptimal PPV (80.1%) and a low NPV (61.1%).Conclusions/SignificanceThe usefulness of the QFT-GIT to diagnose active TB in high TB-endemic countries remains doubtful because like the TST, the QFT-GIT cannot distinguish between LTBI and active TB. Used as single stand-alone tests, both the QFT-GIT and TST have very limited roles in the diagnosis of active PTB. However, the combined use of SM, the TST and QFT-GIT may allow for the exclusion of ATB.
Highlights
Tuberculosis (TB) remains a major global health problem
A total of 400 individuals were enrolled during the one year study period (May 2010-April 2011): 300 pulmonary tuberculosis (PTB) patients and 100 controls
Among the PTB patients, the smear microscopy (SM) was positive in 129/300 that yielded an overall SM sensitivity of 43.0% and an overall SM specificity of 100%
Summary
Tuberculosis (TB) remains a major global health problem It ranks as the second leading cause of death from an infectious disease worldwide, after human immunodeficiency virus (HIV). In 2013, there were an estimated 1 (0.9–1.1) million active TB (ATB) cases in China with 32.5% microbiologically confirmed TB among the total of 847,176 new pulmonary cases [1]. Chinese national guidelines have recommended obtaining three sputum specimens from patients with suspected TB [2]. This re-emphasizes the need of new biomarkers for early diagnosis of active TB [3]. Interferon-release assays (IGRAs) for diagnosing active pulmonary tuberculosis (PTB) are not yet fully validated, in high TB-endemic areas as the People's Republic of China (PRC). The aim of this report was to assess the performance of the QuantiFERONTB Gold In-tube (QFT-GIT) and tuberculin skin test (TST), in addition to microbiological results, as contributors for diagnosing active PTB in the PRC
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