IMMUNODIAGNOSIS OF PULMONARY TUBERCULOSIS BY CONCOMITANT DETECTION OFANTIGEN AND ANTIBODIES OF EXCRETORY-SECRETORY PROTEIN OF MYCOBACTERIUM-TUBERCULOSIS H37RA
An. Lodam et al., IMMUNODIAGNOSIS OF PULMONARY TUBERCULOSIS BY CONCOMITANT DETECTION OFANTIGEN AND ANTIBODIES OF EXCRETORY-SECRETORY PROTEIN OF MYCOBACTERIUM-TUBERCULOSIS H37RA, Journal of Biosciences, 23(1), 1998, pp. 19-23
With a view to diagnosing tuberculosis in populations in endemic areas
, excretory-secretory antigen fraction (Mtb EST-6) of purified Mycobac
terium tuberculosis H37Ra and affinity purified polyclonal antibodies
against Mtb EST were used to detect both antibodies and circulating an
tigen in the sera of patients and disease-free individuals. Indirect s
tick penicillinase ELISA system using Mtb EST-6 detected antigen-speci
fic IgG antibody in 84% of sputum positive, 77% of sputum negative pul
monary tuberculosis patients and 7% of healthy and 11% of subjects wit
h nontuberculosis diseases. Similarly, a sandwich penicillinase ELISA
system using affinity purified anti Mtb EST antibodies detected circul
ating antigen in 83% and 61% of sputum positive and negative pulmonary
tuberculosis subjects. In contrast only 24% of healthy and 18% of dis
ease controls showed seropositivity. Antibody assay showed higher sens
itivity and specificity (83% and 91% respectively) compared to antigen
detection (sensitivity of 79% and specificity of 79%). However, by co
ncomitant use of both assays it was possible to enhance the specificit
y of detection to 98%, though sensitivity was reduced marginally to 70
%. The present study confirms the presence of both antigen and specifi
c antibodies in the circulation during clinical disease and draws atte
ntion to the utility of Mtb EST-6 as a diagnostic marker of pulmonary
tuberculosis.