Quantitative throat-swab culture in the diagnosis of streptococcal pharyngitis in children.

A striking difference in the detection of a heavy growth of Streptococcus pyogenes in throat swabs taken from 1054 children with pharyngitis compared with those from 462 normal children was demonstrated when a standardised technique of quantitative culture was used. In patients with pharyngitis 71% of the isolates were heavy whereas a heavy culture was obtained in only 1-7% of healthy children. Also, a significant correlation between the clinical observations suggestive of streptococcal pharyngitis and the results of culture was confined to those patients whose throat swabs yielded a heavy growth of streptococci. It is concluded that bacteriological examination is of value as a diagnostic test only when the results of culture are quantitatively assessed.