[Value of a rapid test for identification of beta-hemolytic streptococcus antigens in children with streptococcal...

Beta-hemolytic group A streptococcus (Streptococcus pyogenes) is the most common bacterial agent associated with the upper respiratory tract infections in humans. The most frequently group A streptococcus-associated disease is pharyngitis. Males and females are equally affected by group A streptococcus. There is seasonal increase in the prevalence of group A streptococcus-associated pharyngitis. Streptococcal pharyngitis is most prevalent in winter and early spring with higher incidence of disease observed in crowded population such as school children. Early diagnosis and treatment of group A streptococcal pharyngitis has been shown to reduce the severity of symptoms and further complications such as rheumatic fever and glomerulonephritis. The conventional methods used for identification of group A streptococci depend on isolation and identification of the organism on blood agar plates. These methods usually require 18-24 hours of incubation at 37 degrees C. Such delay in identifying the group A streptococcus has often made physicians to administer therapy without first disclosing the etiological agent. Development of immunologic tests, capable of detecting the group A streptococcal antigen directly from the throat swabs, produced rapid test results employed for better treatment of patients. STREP A test is a rapid immunochromatographic test for the detection of group A streptococci from throat swabs or culture. The accuracy of the test does not depend on the organism viability. Instead, group A strep antigen is extracted directly from the swab and identified using antibodies specific for the group A carbohydrates. We compared rapid test with conventional throat swab in 40 children, who met Centor criteria for streptococcal pharyngitis (absence of cough, high fever, purulent pharyngitis, enlarged and painful cervica lymph nodes). Overall congruence of rapid test and culture was 94%. Test is easy to perform and it is recommended as the first diagnostic test for management of children with streptococcal pharyngitis. In children with negative test, but with characteristics highly suggestive of streptococcal infection, throat culture should be performed.