Evaluation of the Directigen 1,2,3 Group A Strep Test for diagnosis of streptococcal pharyngitis

Abstract

The Directigen 1,2,3 Group A Strep Test (DGAST; BBL Microbiology Systems, Cockeysville, Md.) was compared with conventional culture methods for the detection of group A streptococci. Among 327 children, the DGAST had a sensitivity of 75.0%, a specificity of 99.1%, and positive and negative predictive values of 97.5 and 89.3%, respectively, as compared with 48-h culture results. The lower sensitivity (60.0%) in 322 adults was related to the low incidence of group A streptococcal pharyngitis in that population (7.8%). The positive and negative predictive values for adults were 93.8 and 96.7%, respectively. Only 3 of 327 (0.9%) pediatric and 2 of 322 (0.6%) adult specimens yielded uninterpretable results in the DGAST.