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

Karin Rystedt; Katarina Hedin; Mia Tyrstrup; Gunilla Skoog-Ståhlgren; Charlotta Edlund; Christian G Giske; Ronny Gunnarsson; Pär-Daniel Sundvall

doi:10.1080/02813432.2023.2182631

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

Scand J Prim Health Care. 2023 Mar;41(1):91-97. doi: 10.1080/02813432.2023.2182631. Epub 2023 Mar 7.

Authors

Karin Rystedt^{1

2

3

4}, Katarina Hedin^{5

6}, Mia Tyrstrup⁶, Gunilla Skoog-Ståhlgren⁷, Charlotta Edlund⁷, Christian G Giske^{8

9}, Ronny Gunnarsson^{1

2

3}, Pär-Daniel Sundvall^{1

2

3}

Affiliations

¹ Research, Education, Development & Innovation, Primary Health Care, Region Västra Götaland, Sweden.
² General Practice/Family Medicine, School of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
³ Centre for Antibiotic Resistance Research (CARe) at University of Gothenburg, Gothenburg, Sweden.
⁴ Region Västra Götaland, Närhälsan Hentorp Health Care Center, Gröna vagen, Skövde, Sweden.
⁵ Futurum, Region Jönköping County, and Department of Health, Medicine and Caring Sciences, Linköping University, Linköping, Sweden.
⁶ Department of Clinical Sciences in Malmö, Family Medicine, Lund University, Malmö, Sweden.
⁷ Unit for Antibiotics and Infection Control, the Public Health Agency of Sweden, Solna, Sweden.
⁸ Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
⁹ Department of Clinical Microbiology, Karolinska University Hospital, Stockholm, Sweden.

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 POINTSTesting 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 pharyngotonsillitisRADT for GAS is useful in identifying the presence of GAS after recent penicillin V treatment.

Keywords: Streptococcal pharyngotonsillitis; primary care; rapid antigen detection test.

Publication types

Randomized Controlled Trial
Observational Study

MeSH terms

Anti-Bacterial Agents / therapeutic use
Humans
Infant, Newborn
Penicillin V
Pharyngitis* / diagnosis
Pharyngitis* / drug therapy
Pharyngitis* / microbiology
Primary Health Care
Prospective Studies
Streptococcal Infections* / diagnosis
Streptococcal Infections* / drug therapy
Streptococcal Infections* / microbiology
Streptococcus pyogenes

Substances

Penicillin V
Anti-Bacterial Agents

Grants and funding

The study was funded by the Public Health Agency of Sweden. The Healthcare Committee, Region Västra Götaland, Sweden, partially funded the Region Västra Götaland part of the study.