Agreement between rapid antigen detection test and culture for group A streptococcus in patients recently treated for pharyngotonsillitis - a prospective observational study in primary care

• Published in: Scandinavian journal of primary health care 2023, Vol.41 (1), p.91-97
• Main Authors: Rystedt, Karin, Hedin, Katarina, Tyrstrup, Mia, Skoog-Ståhlgren, Gunilla, Edlund, Charlotta, Giske, Christian G., Gunnarsson, Ronny, Sundvall, Pär-Daniel
• Format: Article
• Language: English
• Subjects: Agreements; Allmän medicin; Anti-Bacterial Agents - therapeutic use; Antibiotics; Antigens; Bacteria; Clinical Medicine; Clinical trials; Culture; Family Medicine; Health care; Humans; Infant, Newborn; Infectious Medicine; Infektionsmedicin; Klinisk medicin; Medical and Health Sciences; Medicin och hälsovetenskap; Observational studies; Original; Penicillin; Penicillin V; Pharyngitis - diagnosis; Pharyngitis - drug therapy; Pharyngitis - microbiology; Primary care; Primary Health Care; Prospective Studies; rapid antigen detection test; Streptococcal Infections - diagnosis; Streptococcal Infections - drug therapy; Streptococcal Infections - microbiology; Streptococcal pharyngotonsillitis; Streptococcus infections; Streptococcus pyogenes; Tests
• ISSN: 0281-3432; 1502-7724; 1502-7724
• DOI: 10.1080/02813432.2023.2182631

The aim was to compare rapid antigen detection test (RADT) and throat culture for group A streptococci (GAS) among patients recently treated with penicillin V for GAS pharyngotonsillitis. The study was a secondary analysis within a randomized controlled trial comparing 5 versus 10 days of penicillin V for GAS pharyngotonsillitis. Patients were recruited at 17 primary health care centres in Sweden. We included 316 patients ≥ 6 years of age, having 3-4 Centor criteria, a positive RADT and a positive throat culture for GAS at inclusion, and also having a RADT and throat culture for GAS taken at a follow-up visit within 21 days. RADT and conventional throat culture for GAS. This prospective study showed 91% agreement between RADT and culture at follow-up within 21 days. Only 3/316 participants had negative RADT with a positive throat culture for GAS at follow-up, and 27/316 patients with positive RADT had a negative culture for GAS. Log rank test did not reveal any difference in the decline over time of positive tests between RADT and throat culture (p = 0.24). Agreement between RADT and throat culture for GAS at the follow-up was not associated with treatment duration, number of days from inclusion until follow-up, throat symptoms at follow-up, gender, or age. RADT and culture for GAS agreed to a high extent also after recent penicillin V treatment. RADT for GAS means a low risk for missing the presence of GAS. KEY POINTS Testing for group A streptococci (GAS) before antibiotic treatment can reduce antibiotic prescription for pharyngotonsillitis. It has been proposed that rapid antigen detection tests (RADT) for group A streptococci after recent penicillin V treatment may be falsely positive due to possible persisting antigens from non-viable bacteria. The decline of the presence of GAS was similar between RADT and conventional throat culture in patients who had recently completed penicillin V treatment for GAS pharyngotonsillitis RADT for GAS is useful in identifying the presence of GAS after recent penicillin V treatment