- Last Update On : 2013-01-13
Group A beta-hemolytic streptococcus (GAS, S. pyogenes) is responsible for up to 30% of cases of acute pharyngitis. The clinical features of pharyngitis caused by group A strep include purulent exudate, fever, and anterior cervical adenopathy. Beta-hemolytic streptococci groups C & G can cause pharyngitis with symptoms and signs that are indisitinguishable from group A strep infections, but are more commonly found in adolescents and young adults.
The mainstay of diagnosis for group A strep pharyngitis is rapid antigen testing of throat swabs. The obvious advantage of rapid antigen testing is the immediate availability of results and the ability to perform testing in the clinic setting. However, a major disadvantage of these tests is less than optimal sensitivity, so that culture back-up of negative tests is essential. Culture is also necessary to identify the presence of group C or G streptococci, which are not detected by rapid antigen tests. Unfortunately, final cultur