Diagnosis of group A beta-hemolytic Streptococcus using clinical scoring criteria, Directigen 1-2-3 group A streptococcal test, and culture.

Cultures for group A beta-hemolytic Streptococcus were performed on 806 patients presenting with a sore throat to five urgent care centers. The accuracies of a clinical scoring system and of a liposomal in-office direct test for Streptococcus were compared with culture results. The Directigen 1-2-3 group A streptococcal test had a sensitivity of 67%, a specificity of 85%, a positive predictive value of 61%, and a negative predictive value of 89% compared with culture. The scoring system had a sensitivity of 26%, a specificity of 94%, a positive predictive value of 58%, and a negative predictive value of 79%. Using a combination of the direct test results and the clinical score did not improve the accuracy significantly over the use of either alone. The rates of delayed treatment, unnecessary treatment, and increased costs were compared using different combinations of the clinical scoring system, the in-office streptococcal test, and culture. Neither the Directigen 1-2-3 group A streptococcal test nor the clinical score can replace culture in the diagnosis of group A beta-hemolytic streptococcal pharyngitis.