Impact of rapid antigen tests for group A streptococcal pharyngitis on physician use of antibiotics and throat cultures.

Using case scenarios and an interview guided by a decision tree diagram, the clinical strategies of 150 physicians (50 private pediatricians, 50 health maintenance organization pediatricians and 50 pediatric residents) were assessed for the management of pharyngitis under three conditions: (1) no rapid antigen detection test available for diagnosing Group A streptococcal disease; (2) antigen test result available in 20 minutes; and (3) antigen test result available in 4 hours. The sensitivity of the antigen test was designated as 0.95 if the growth of rare or few Group A streptococci on throat culture was discounted and 0.82 if any growth was considered significant, and the specificity was set at 0.98. In a standardized pediatric case with a prior probability of Group A streptococcal disease of 0.58, 84% of clinicians would order a 20-minute test and 39% would order a 4-hour test. The 20-minute test would reduce throat culture use by 54%, reduce the proportion of patients exposed to antibiotics from 86% to 65% and reduce total antibiotic treatment days by 13.8%. Effects would be less pronounced for a low probability case or if results of antigen testing were not available for 4 hours. Provided a test with a documented high sensitivity and specificity were used, a rapid antigen test with results promptly available would substantially reduce throat culture use and unnecessary antibiotic exposures in children with a moderate prior probability of streptococcal disease.