Comparative Evaluation of Specific Antibody against Mycobacterium tuberculosis ESAT-6 Recombinant Antigen in Healthy Subject with Positive and Negative Skin Test.

. The present study aimed to measure specific antibody serum levels against the early secretory antigenic target 6 kDa (ESAT-6) recombinant protein in healthy people and compare it to TB patients. The target population included 27 TB patients and 87 healthy individuals with no clinical TB symptoms. The healthy population was divided into two groups, including positive purified protein derivative (PPD) and negative PPD (35 and 52 people, respectively), using the Tuberculin skin test. The specific antibody level against the ESAT-6 recombinant antigen and the PPD protein was measured using an indirect Enzyme-Linked Immunosorbent Assay (ELISA) test. The results of the study showed that the majority of the healthy population with no symptoms of clinical TB and having negative skin test results did not have antibodies against the recombinant ESAT-6 (98%) and PPD (96%) antigens. On the other hand, there was a high level of the specific antibody of the ESAT-6 recombinant and PPD antigens in TB patients (77%). It is notable that in people with positive skin test results, the level of the antibody against the ESAT-6 recombinant antigen and PPD antigen was 94%. The results demonstrated that the ELISA method based on the measurement of antibodies against the ESAT-6 recombinant antigen can be a proper diagnostic method for rapid and accurate screening of healthy from infected people.