Evaluation of antibody level to purified mycobacterial antigens for identification of tuberculous infection.

Alamelu Raja; Acharyulu, G.S.; Selvaraj, R.; Abdul Khudoos

Biomedicine; 2001; 21; 63-69.           

For the identification of tuberculous infection, tuberculin test is the only tool that is available now. But this test is known to have practical disadvantages, in addition to the lack of high specificity and sensitivity. The role of antibody levels to mycobacterial antigens, for identifying tuberculous infection has therefore been investigated, using enzyme linked immunosorbent assay (ELISA). The criteria for dignosing tuberculous infection was based on comparing the distribution of antibody levels in the definitely infected and non-infected groups. The test showed 73% sensitivity and 79% specificity. Even purified antigens like antigen 6 (30 kDa) and recombinant 38 kDa (r38 kDa) are not satisfactory (sensitivity = 61-75%; specificity = 63-72%). The findings of this investigation indicate that antibody levels are not useful in diagnosing tuberculous infection. However, in view of the fact that serolgocial assays have more practical advantages than skin test and devoid of complications due to prior vaccination, further attempts are worthwhile to develop antigen / antibody detection assays with carefully chosen antigen (s).

Key words : M. tuberculosis , Mantoux test, tuberculous infection, ELISA, r38 kDa, Antigen 6

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