Diagnostic potential of fractionatedMycobacterium tuberculosis H(37)R(a) excretory-secretory (EST-DE(1)) antigen in pulmonary tuberculosis.

Tuberculosis is emerging as a major public health problem in developing and developed world. Early and precise diagnosis is of prime importance in successful control of infection. Indirect ELISA with penicillinase as marker was developed using purifiedM. tuberculosis excretory-secretory (EST-DE(1)) antigen for detecting IgG antibodies in pulmonary tuberculosis. The assay System gave a overall sensitivity of 82% for both smear positive and smear negative pulmonary tuberculosis cases with a specificity of 84%. The positive and negative predictive values were 75% and 88% respectivaly. Further studies with EST-DE(1) antigen revealed that, it contains two of the active antigen fractions of Mtb EST antigen i.e. Mtb EST-4 (56-68 KDa) and Mtb EST-6 (37-45 KDa), as demonstrated by inhibition ELISA. Reactivity with monoclonal antibodies HGT 3a showed the presence of 38 KDa molecule in EST-DE(1) antigen.