Performance of ESAT-6 and CFP-10 in diagnosis of tubercular infection

Background Diagnosis of latent tuberculosis infection (LTBI) is currently based on the tuberculin skin test. The Enzyme-linked immunospot assay (ELISPOT) is a new blood test to diagnose LTBI. Genomic analyses have enabled the identification of specific M. tuberculosis proteins (ESAT-6 and CFP-10). The use of such proteins in vitro makes it possible to detect the presence of T lymphocytes circulating as a result of a specific stimulus. The aim of this study is to compare the ELISPOT and the tuberculin skin test for detecting LTBI in patients with tuberculosis. Patients and Methods 452 blood samples were taken: 150 subjects as control groups and 302 subjects with TB-like symptoms and analysed. The T effector lymphocyte assay was performed by T-SPOT TB (Oxford Immunotec). Results Among 150 healthy subjects (control groups) the Mantoux test and the in vitro test identified 0 subjects, 23 (15,3%) were still positive in the Mantoux test, but were negative in the in vitro assay. While, 127 (84,7%) were negative in both immunological tests. Of the group of 302 patients with unidentified fever, 126 (41.7%) were positive in both immunological tests. Lastly 126 (41.7%) were negative for both tests. 25 cases were positive in the Mantoux test alone (8.3%). Conclusions Compared with the tuberculin skin test, the ELISPOT appears to be at least as sensitive for diagnosis of LTBI in patients with tuberculosis