Comparative evaluation of two indigenously developed tests for rapid detection of group-A streptococci directly from throat swabs.

ABSTRACT

The efficacy of two indigenously developed rapid tests, latex agglutination and antibody capture assay (a colour immunochromatographic assay) to detect group A Streptococcus pyogenes (GAS) was evaluated in comparison with the traditional culture method ('Gold Standard') in both asymptomatic children (1500) and symptomatic patients (233). Throat swabs were taken in duplicate and rapid tests performed on one swab and culture on the other. Both latex agglutination and antibody capture assays showed a sensitivity of 100 per cent and specificity of > 98 per cent as compared to culture and isolation in symptomatic patients. However, among asymptomatic carriers sensitivity of 100 per cent and 87.5 per cent and specificity > 95 per cent were observed for latex agglutination and antibody capture assays respectively. Latex agglutination showed no false negative results and sensitivity was not affected by low beta-haemolytic counts in asymptomatic children. The rapid tests described here will help in the detection and thereby the management of GAS infection.