Value of ELISA using antigen 60 for the diagnosis of tuberculosis in children

We evaluated the possible value of enzyme-linked immunosorbent assay (ELISA) using antigen 60 (A60) for improved diagnosis of tuberculosis in children. Results obtained in 31 children with active tuberculosis and in 16 patients with tuberculous infection without disease were compared with the results of 198 control subjects with no mycobacterial disease. In control children, anti-A60 IgG increased with age and the optical density (OD) in ELISA assays rose from .079 +/- .053 (OD +/- SD) in children younger than 5 years old to 0.146 +/- 0.082 OD in children older than 5 years. In control subjects younger than 2 years old, IgG OD values were significantly higher in BCG-vaccinated children than in nonvaccinated children. At a chosen specificity of 98 percent, a positive serodiagnosis was observed in 68 percent of children with clinically active tuberculosis. In these children with active disease, smears were positive in only 26 percent of cases and mycobacterial cultures yielded the organism in 45 percent of cases. None of the infected children without disease had high IgG OD values. IgM measurements were also evaluated. Mean values from control and diseased children overlapped, leading to a low sensitivity (19 percent) in children with clinically tuberculosis active. We conclude that anti-A60 IgG measurement is a rapid and low-cost technique that enhances the diagnosis of clinically active tuberculosis in children and may distinguish recent infection without disease from infection with disease.