Detection of mycobacterial antigens in sputum by an enzyme immunoassay

Abstract

An enzyme immunoassay (EIA) for the detection of mycobacterial antigens in sputum was evaluated. The system utilises commercially available anti-BCG immunoglobulin. BCG protein standard was used as positive control. Thirty-nine patients with culture-proven pulmonary tuberculosis were tested. The EIA was positive in 24 of 29 patients with positive smears and cultures, giving a sensitivity of 86.2%. It was also positive in six of ten patients with smear-negative culture-positive disease, resulting in a sensitivity of 60% in this group. In another 176 patients with different nontuberculous pulmonary infections, only nine were positive by EIA, giving a specificity of 94.9%. The high sensitivity and specificity of the assay make it a useful tool for the early diagnosis of pulmonary tuberculosis.