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  Kim34*   

1 Department of Laboratory Medicine, Daewoo General Hospital, Geoje
2 Department of Pediatrics,Changwon Fatima Hospital, Changwon
3 Department of Laboratory Medicine, Gyeongsang National University Changwon Hospital, Changwon
4 Gyeongsang National University, Gyeongsang Institute of Health Sciences, Jinju

* Corresponding author: Tel: +82-55-214-3072, Fax: +82-55-214-3087, E-mail: sjkim8239@hanmail.net

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.

Figures & Tables

Fig. 1. Distribution of age and sex of STANDARD F Strep A Ag FIA positive patients.