The serodiagnosis of tuberculosis in children: an evaluation of an ELISA test using IgG antibodies to M. tuberculosis, strain H37 RV.

An enzyme-linked immunosorbent assay (ELISA) for detecting serum IgG antibodies to an autoclaved suspension of Mycobacterium tuberculosis H37 RV was evaluated as a diagnostic tool in 132 clinical cases of childhood tuberculosis. The mean (SD) optical density value in these patients was 0.115 (0.122) compared with 0.022 (0.017) in the control group of patients who had non-tuberculous acute respiratory tract infections. Using as a cut-off level the mean of the control plus 2 standard deviations, the test sensitivity was 62% and the specificity was 98% in all the patients with a clinical diagnosis of tuberculosis. In the culture-positive group (n = 35), the sensitivity was 69%. A positive correlation was shown between the optical density levels and increasing age and chronicity of infection but not with respect to tuberculin skin reactivity, nutritional status and the duration of prior therapy. In addition, BCG vaccination (presence of a scar) did not affect the ELISA result. We conclude that this ELISA test is a useful diagnostic test in children.