title: Evaluating the American Academy of Pediatrics diagnostic standard for Streptococcus pyogenes pharyngitis: backup culture versus repeat rapid antigen testing.
abstract: OBJECTIVE
  The American Academy of Pediatrics recommends that all negative rapid diagnostic tests for Streptococcus pyogenes pharyngitis be backed up by culture, which creates a dilemma for clinicians who must make treatment decisions without complete diagnostic information at the time of visit. The use of a follow-up serial rapid antigen test instead of a follow-up culture would provide a more timely result.
  
  
  METHODS
  Two swabs were collected from children who were suspected of having S pyogenes pharyngitis. Each swab was used for a culture and an OSOM Ultra Strep A Test rapid antigen test. The gold standard of comparison was defined as the identification of S pyogenes on either of the 2 culture plates. Three diagnostic strategies were evaluated: a single rapid antigen test, a rapid antigen test with follow-up rapid antigen test (rapid-rapid), and a rapid antigen test with follow-up culture (rapid-culture).
  
  
  RESULTS
  A total of 210 (23.7%) of 887 throat cultures with matched data were identified with S pyogenes. A single rapid antigen test had a sensitivity of 87.6% (95% confidence interval [CI]: 83.2%-92.1%), the sensitivity of the rapid-rapid follow-up was 91.4% (95% CI: 87.6%-95.2%), and the sensitivity of the rapid-culture follow-up was 95.7% (95% CI: 93.0%-98.5%), which was significantly higher than the others. As shown in Fig 1, when these test strategies were evaluated on a subgroup with clinical symptoms commonly associated with S pyogenes pharyngitis, the sensitivities all increased and were no longer significantly different. None of the strategies reliably exceeded a 95% sensitivity threshold.
  
  
  CONCLUSIONS
  The American Academy of Pediatrics strategy for S pyogenes detection in children with pharyngitis, requiring a backup culture for those with negative antigen tests, was not exceeded by any other test strategy; however, a rapid-rapid diagnostic strategy may approximate it with the use of judicious clinical selection of patients.
authors.affiliation: Department of Epidemiology, University of Colorado Health Sciences Center, Denver, Colorado, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Gieseker
authors.forename: Martha H
authors.initials: MH
authors.lastname: Roe
authors.forename: Todd
authors.initials: T
authors.lastname: MacKenzie
authors.forename: James K
authors.initials: JK
authors.lastname: Todd
mesh_terms: D000942:Antigens, Bacterial / Q000032:analysis* / Q000276:immunology; D015373:Bacterial Typing Techniques / Q000592:standards*; D002648:Child; D006801:Humans; D007118:Immunoassay / Q000592:standards; D010612:Pharyngitis / Q000175:diagnosis* / Q000382:microbiology; D011446:Prospective Studies; D011933:Reagent Kits, Diagnostic / Q000592:standards; D012680:Sensitivity and Specificity; D012955:Societies, Medical / Q000592:standards; D013048:Specimen Handling / Q000592:standards; D013290:Streptococcal Infections / Q000175:diagnosis* / Q000382:microbiology; D013297:Streptococcus pyogenes / Q000254:growth & development* / Q000302:isolation & purification*
chemical_list: D000942:Antigens, Bacterial; D011933:Reagent Kits, Diagnostic