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.
Institute for Tuberculosis Research, The Second Affiliated Hospital of Chinese PLA General Hospital, Beijing 100091, China. wu-xueqiong@263.net
Xueqiong
X
Wu
Qiaoke
Q
Li
Yourong
Y
Yang
Chuiying
C
Zhang
Juan
J
Li
Junxian
J
Zhang
Yan
Y
Liang
Hongbing
H
Cheng
Jingzhuan
J
Zhang
Lin
L
Zhu
Guangyu
G
Zhang
Lan
L
Wang
D000942:Antigens, Bacterial / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D002681:China; D003001:Cloning, Molecular; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D015870:Gene Expression; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D008889:Military Personnel; D010560:Personnel Selection / Q000379:methods*; D014374:Tuberculin Test / Q000379:methods*; D014376:Tuberculosis / Q000175:diagnosis*
D000942:Antigens, Bacterial; D001426:Bacterial Proteins; C117940:CFP-10 protein, Mycobacterium tuberculosis; C093276:ESAT-6 protein, Mycobacterium tuberculosis