Evaluation of rapid antigen test in child patients with group A streptococcal tonsillopharyngitis

Abstract

Objective: The most frequently encountered diseases in childhood are the upper respiratory tract infections. Although in our country the most common agent of tonsillopharyngitis is viral, it ranks high in rates of unnecessary use of antibiotics. Streptococcus pyogenes, which is known as Group A streptococcus, is the most common bacterial agent of acute tonsillopharyngitis. The rate of Group A streptococcus causing cases of tonsillopharyngitis in children varies between 20%-40%. The gold standard for diagnosis of Group A streptococcus is the throat culture test. However, faster methods have been developed as it takes 24-48 hours to produce results. This study aims to evaluate the effectiveness of the rapid antigen test by comparing the results obtained from the rapid antigen detection test and throat culture test. Methods: In this study, the results from 297 throat swab samples that had been sent to our laboratory with a diagnosis of tonsillopharyngitis, which belonged to patients who had presented to the pediatric diseases clinic between the dates of February 2017-January 2018, were retrospectively evaluated. With one of the samples, inoculation to sheep blood agar was performed for the throat culture test, and simultaneously, the rapid antigen test (TOYO, Turklab) was done on the other sample. For suspected growth of beta hemolytic colonies in the culture, bacitracin susceptibility and PYR tests were also carried out. Results: A total of 297 patients were inspected with both culture test and rapid antigen test. The culture test was positive in 55 (18.5%) of the samples, and the rapid antigen test in 51 (17.1%). The rapid antigen test was determined to have a sensitivity of 83.6%, specificity of 97.9%, positive predictive value of 90%, negative predictive value of 96.3%, and accuracy of 95%. Conclusion: The utilization of the rapid antigen test for the diagnosis of Group A streptococcus tonsillopharyngitis will help restrain unnecessary use of antibiotics. The prevention of resistance development with proper use of antibiotics is of importance. Based on the results of our study, the specificity of the rapid test is high, but its sensitivity is lower. For this reason, confirming negative results from the rapid antigen test with the culture test is necessary with regard to undertreatment and complications. © 2019, Refik Saydam National Public Health Agency (RSNPHA).