Using the TBAg/PHA Ratio in the T-SPOT(®).TB Assay to Distinguish TB Disease from LTBI in an Endemic Area

Overview

Journal Int J Tuberc Lung Dis

Specialty Pulmonary Medicine

Date 2016 Mar 13

PMID 26970158

Citations 20

Authors

F Wang

H-Y Hou

S-J Wu

Q Zhu

M Huang

B Yin

J Huang

Y-Y Pan

L Mao

Z-Y Sun

Affiliations

Soon will be listed here.

Abstract

Setting: An important limitation of the T-SPOT(®).TB assay is its inability to distinguish active tuberculosis (TB) from latent tuberculous infection (LTBI).

Objective: We proposed a new calculation method for the T-SPOT assay and assessed its effect on distinguishing active TB from LTBI.

Design: A total of 162 active TB patients and 97 LTBI individuals were diagnosed according to conventional tests and the T-SPOT assay.

Results: The results of early secreted antigenic target 6 (ESAT-6) and culture filtrate protein 10 (CFP-10) in T-SPOT cannot be recommended for distinguishing TB from LTBI. The number of phytohaemagglutinin (PHA) spot-forming cells (sfc) in the T-SPOT assay was reduced in active TB patients. The ESAT-6/PHA or CFP-10/PHA ratios in active TB patients were significantly higher than in individuals with LTBI. Using 0.295 as the threshold ratio of Mycobacterium tuberculosis-specific antigen (TBAg) sfc to PHA sfc (TBAg/PHA ratio, the larger of ESAT-6/PHA and CFP-10/PHA), the sensitivity and specificity were 82.1% and 90.7% in distinguishing active TB from LTBI. The TBAg/PHA ratio might also be used to monitor the effect of anti-tuberculosis treatment.

Conclusions: Calculating the TBAg/PHA ratio might have the potential to diagnose active TB and distinguish TB disease from LTBI.

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