Annals of Clinical Microbiology, The official Journal of the Korean Society of Clinical Microbiology

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pISSN 2288-0585 eISSN 2288-6850

Performance Evaluation of STANDARD F Strep A Ag FIA for Diagnosis of Group A Streptococcal Pharyngitis

Original article

Annals of Clinical Microbiology (Ann Clin Microbiol) 2020 September, Volume 23, Issue 3, pages 177-184.

https://doi.org/10.5145/ACM.2020.23.3.1

Performance Evaluation of STANDARD F Strep A Ag FIA for Diagnosis of Group A Streptococcal Pharyngitis

Seon A Jo1, Sang Hyuk Ma2, Seungjun Lee3, Sunjoo Kim3,4
1Department of Laboratory Medicine, Daewoo General Hospital, Geoje, 2Department of Pediatrics, Changwon Fatima Hospital, Changwon,3Department of Laboratory Medicine, Gyeongsang National University Changwon Hospital, Changwon, 4Gyeongsang National University, Gyeongsang Institute of Health Sciences, Jinju, Korea

Abstract

Background: Pharyngitis is one of the most common conditions encountered in primary health care facilities. Accurate differentiation of group A streptococcus (GAS) infection from viral infection is difficult. The STANDARD F Strep A Ag FIA (SD BIOSENSOR, Korea) is a rapid antigen detection test (RADT) that has been recently developed for diagnosing GAS pharyngitis. In this study, we evaluated the diagnostic performance of the STANDARD F Strep A Ag FIA and compared the results between the RADT and conventional throat culture.

Methods: Throat swab samples were obtained from a total of 372 children presenting pharyngitis symptoms in five pediatric clinics in Changwon, Korea from July 2018 to October 2019. A comparative study between STANDARD F Strep A Ag FIA and Sofia Strep A FIA (Quidel, USA) was performed. Two throat swabs were taken simultaneously from each patient for RADT. The third throat swab was stored in a transport tube containing Stuart’s transport medium for culture. Performance and kappa index of STANDARD F Strep A Ag FIA were evaluated.

Results: GAS infection was detected in 29.3% (109/372) patients, using the STANDARD F Strep A Ag FIA. The sensitivity, specificity, positive predictive value, and negative predictive value were 95.0%, 95.2%, 88.1%, and 98.1%, respectively. The STANDARD F Strep A Ag FIA showed an excellent concordance rate of 96.5% and a kappa value of 0.89 compared to Sofia Strep A FIA.

Conclusion: The STANDARD F Strep A Ag FIA demonstrated an excellent performance along with Sofia Strep A FIA for the diagnosis of GAS pharyngitis.

Keywords

Group A streptococcus, Pharyngitis, Rapid antigen test, Streptococcus pyogenes, Tonsillitis