Investigation on latent tuberculosis infection in the new recruits with enzymelinked immunospot assay

Abstract:

ObjectiveTo study the latent tuberculosis infection (LTBI) in the new recruits with enzymelinked immunospot assay (ELISPOT), and evaluate the value of ELISPOT on the detection of LTBI .MethodsA total of 366 new recruits were intradermally injected with purified protein derivative (PPD) ,and detected with ELISPOT assay with recombinant CFP10/ESAT6 fusion protein (rCFP10/ESAT6) as a stimulus. New recruits who were ELISPOT and PPDnegative were vaccinated by intradermal injection with Bacillus CalmetteGuerin (BCG) vaccine, they were detected by PPD skin test and ELISPOT assay again 10 months later.ResultsAmong 366 new recruits , the positive rate of PPD skin test and ELISPOT assay was 44.81% and 31.69%, respectively. Of 202 PPDnegative and 164 PPDpositive new recruits, 53 (26.24%) and 63 (38.41%) were ELISPOT positive, respectively， overall consistency between two tests was 57.92% (212/366), the difference was statistically significant(χ2=14.34，P<0.001). Among new recruits with BCG vaccination , PPD and ELISPOTpositive rate was 58.53% (127/217) and 29.03% (63/217) respectively, spot forming cell (SFC) were 32.44±26.52; Among new recruits without BCG vaccination , PPD and ELISPOTpositive rate was 24.83% (37/149) and 35.57% (53/149) respectively, SFC were 41.81±30.48. 78.18% of 110 new recruits vaccinated by BCG vaccine 10 months later were PPDpositive, but all of they were ELISPOTnegative. ConclusionELISPOT technique has high specificity and sensitivity for screening TB infection.