Study of respiratory symptoms among sputum positive

j -
Immunological techniques in the diagnosis of mycobacterial
infection
Engvall and Perlman (1972), were the first who described the
ELISA, they reported that it is very sensitive and simple method for
detection and measurement of antibodies in sera. Nassau et aI. (1976),
used ELISA for diagnosis of tuberculosis using concentrated culture filtrate
of M.TB using concentrated as antigen. They found that 84% of sputum
positive cases were positive by that test and only 8% false positive
reactions were observed. They also concluded that serum dilution of I: 100
gave good discrimination between sera from tuberculous patients and
controls. They reported that ELISA proved to be satisfactory for detection
of antimycobacterial antibodies. They postulated that the use of specific
antigen should increase the specificity ofthe test.
The major limiting factor in the serodiagnosis of tuberculosis is that
no single species specific antigen of mycobacterium tuberculosis has been
shown to be significantly elevated in all cases ofactive tuberculosis. On the
contrary, most ofthe antibody response in tuberculosis is directed towards
those antigens common to all mycobacteria and, to some extent, present in
other genera. Sensitive assays show that virtually all individuals have such
antibodies (Grange et aI., 1980). In spite of that many research
laboratories have demonstrated that ELISA measurement ofIgG antibody
to mycobacterial antigen can be used for the serologic diagnosis of
tuberculosis (Shim et aI., 1989).
Other serodiagnostic techniques including radio-immunoassay (RIA)
and inhibition of monoclonal antibodies, had less extensive studies but
appear promising (ATS, 1990).
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