Use of IFN-γ release assay in latent tuberculosis infection diagnosis in general and HTV-infected populations

Objective To assess the validity of a newly developed in-house ELISPOT IFN-γ release assay (IGRA) for the detection of latent tuberculosis infection among HIV infected individuals. Methods In-house ELISPOT assay were performed, together with a tuberculin skin test in 205 health controls and 110 HIV infected individuals , who had no signs of active tuberculosis at time of enrolment . Results Using the ELISPOT assay, positivity rates for the 205 health controls, 110 HIV infected individuals and 47 AIDS patients on highly active antiretrovial therapy (HAART) were 7. 3% , 24.5% , 29. 8% , respectively. These results indicated that the positive rates obtained from HIV infected individuals (include patient on HAART) was significantly higher than health controls( P ＜ 0.001). We found no significant correlation between the CD4 cell count and positivity of ELISPOT assay (P ＞0.05 ). The proportion of subjects with a positive response to ELISPOT assay were higher than the proportion of tuberculin skin test(TST) responders(P＜0.0001) in HIV infected individuals. Conclusion Our study indicates that IGRA using M. tuberculosis specific antigens are likely to retain their validity for the diagnosis of LTBI among HIV positive individuals. Key words: Human immunodeficiency virus;  Latent tuberculosis infection;  IFN-γ release assay;  Enzyme-linked immunospot assay;  Tuberculin skin test