Latent tuberculosis infection amongst new recruits to the Chinese army: comparison of ELISPOT assay and tuberculin skin test.

BACKGROUND

In China, latent tuberculosis infection (LTI) is frequent. To protect the health of soldiers and monitor TB infection, new recruits were routinely examined for LTI by tuberculin skin testing (TST). This is the first report on the extent of LTI in the Chinese army comparing TST and enzyme-linked immunospot (ELISPOT) assay.

METHODS

New recruits to the army were interviewed, routinely examined and injected intradermally with purified protein derivative (PPD) in March 2007. At the same time, 100 male soldier volunteers were detected with ELISPOT assay using recombinant CFP-10/ESAT-6 fusion protein (rCFP-10/ESAT-6) as a stimulus.

RESULTS

The prevalence of LTI, as estimated by TST and ELISPOT assay, was 41% and 21% of new recruits, respectively. Vaccination scars on the arms could be found in 83% of volunteers with positive TST and 19% of volunteers with negative TST. Five individuals with strongly positive TST of whom 2 had negative ELISPOT were not given chemotherapy, and were observed for 20 months. None developed active TB.

CONCLUSIONS

The prevalence of LTI in new recruits to the Chinese army is not as high as previously reported. ELISPOT technique may be the most accurate screening method for the TB infection in China, which was not interfered by BCG vaccination.