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. (2nd January 2023)

• Record Type: Journal Article
• Authors: Rystedt, Karin; Hedin, Katarina; Tyrstrup, Mia; Skoog-Ståhlgren, Gunilla; Edlund, Charlotta; Giske, Christian G.; Gunnarsson, Ronny; Sundvall, Pär-Daniel
• Is Part Of: Scandinavian journal of primary health care. Volume 41:Number 1(2023)
• Page Start: 91
• Page End: 97
• Publication Date: 2023-01-02
• Subjects: Streptococcal pharyngotonsillitis -- rapid antigen detection test -- primary care; Primary health care -- Periodicals; 610
• DOI: 10.1080/02813432.2023.2182631
• Languages: English
• ISSNs: 0281-3432

Abstract

Abstract: Objective: 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. Design and setting: 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. Subjects: 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. Main outcome measures: RADT and conventional throat culture for GAS. Results: 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. Conclusion: 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