Tehran University of Medical Sciences Journal of Medical Bacteriology 2251-8649 1 3-4 2015 10 12 37 43 EN Mohammad Morad-Farajollahi Department of Biotechnology and Cellular and Molecular Research Center, Tehran University of Medical Sciences, Tehran,IR Iran. Sepideh Hamzehlou Department of Biotechnology and Cellular and Molecular Research Center, Tehran University of Medical Sciences, Tehran,IR Iran. 2015 10 12 2015 10 12 Background: Tuberculosis is a crucial health problem. Establishing a rapid, reliable and still inexpensive diagnostic method for tuberculosis seems to be substantial in developing countries where TB has very high incidence rate . Methods:  An Indirect  Enzyme-linked  immunosorbent  Assay (ELISA)  was established to detect serum antibodies against Mycobacterium  tuberculosis. Three kinds of antigens were used to prepare the solid phase for antibody as- say including: purified protein derivative (PPD), M. tuberculosis Bacilli, and Mycobacterium  bovis Bacillus  Calmette  Guerin  (BCG).  Sera  of two main following groups were investigated in this study: sera samples from smear- positive, culturepositive and Tuberculin Skin Test-positive TB patients and sera samples from smear-negative, culture negative and TST-negative healthy individuals. Results: Among the antigens used, BCG produced higher sensitivity and specificity in the assay. With PPD as the solid phase, higher sensitivity but low er specificity was observed in comparison with BCG. Both, low response and noise (non-specific binding) were observed with TB bacilli as the solid phase in the assay. Conclusion: Using BCG solid phase system in this method resulted in higher sensitivity in comparison to single antigen solid phase systems. In addition, we were able to circumvent  the problem of non-specific  bindings in more popular multi-antigenic solid systems such as PPD. By using this new indi- rect ELISA, a rapid, reliable and still inexpensive diagnosis of tuberculosis might be possible. Although, further investigations  are required to confirm our result. https://jmb.tums.ac.ir/index.php/jmb/article/view/23 https://jmb.tums.ac.ir/index.php/jmb/article/download/23/19