Group A streptococcal antigen detection in schoolchildren

The objective of the study was to determine the correlation between group A streptococcal antigen detected from throat swabs with the culture results. A total of 1457 children had two swabs taken simultaneously, and culture and antigen detection were performed. There was a good correlation between antigen detection and isolation rates. In all, 225 strains of group A streptococcus were isolated; 53 (57.6%) were from the 92 children with high antigen positivity, 68 (55.7%) were from the 122 children with medium antigen positivity and 77 (25.4%) were from 303 children with low antigen positivity; only 27 (2.9%) were from the 940 children with no antigen detected. We postulate that those who are antigen-positive, culture-negative carry the organisms in their throats, but they may be missed on culture because of the small number carried.