Role of rapid antigen detection test for the diagnosis of group-A ß-hemolytic streptococcus in patients with pharyngotonsillitis

One of the most common conditions encountered in the out-patient setting is acute pharyngitis. Group A Streptococcus (GAS) accounts for 15%-30% of cases of sore throat particularly in children under 15 years old. Rapid antigen testing (RADT) is an alternative diagnostic method to detect GAS pharyngitis. This study was done to evaluate the agreement between RADT whereby BIONEXIA® Strep A Plus (BioMérieux, France) kit was used and throat culture in the diagnosis of GAS pharyngitis in children presented with a sore throat. One hundred and ten children from a primary health care clinic with sore throat were included in this study. All children were evaluated based on McIsaac scoring and throat swab samples were taken for both throat culture and RADT testing. The prevalence of GAS pharyngitis by RADT in this study was 7.3% over one year. A higher incidence of GAS pharyngitis was noted in the school-aged children than the preschool-age children. There was no correlation between cough, lymph node enlargement, and tonsillar enlargement in predicting GAS pharyngitis. The sensitivity and specificity of RADT were 100% and 98%, respectively, when taking throat culture as a gold standard. A good agreement between RADT and throat culture was achieved (k=0.848). McIsaac scoring was noted to have good predictability for GAS pharyngitis with AUC=0.82. In conclusion, the rapid streptococcal antigen detection test showed excellent sensitivity and specificity and detecting GAS from the throat swab samples. Thus, it can be used to aid in the diagnosis of group A Streptococcal pharyngitis and could reduce the overuse of antibiotics. McIsaac score has also proven to be useful as a screening tool for bacterial pharyngitis.

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Modern understanding about the role of group A β -hemolytic streptococcus in acute tonsillitis

Journal Infectology ◽

10.22625/2072-6732-2021-13-4-66-71 ◽

2021 ◽

Vol 13 (4) ◽

pp. 66-71

Author(s):

N. T. Mirzoev ◽

S. N. Sidorchuk ◽

Yu. I. Bulan’kov ◽

K. V. Kas’janenko

Keyword(s):

Predictive Value ◽

Bacterial Culture ◽

Detection Method ◽

Throat Swab ◽

Diagnostic System ◽

Antigen Detection ◽

Acute Tonsillitis ◽

Hemolytic Streptococcus ◽

Streptococcal Antigen ◽

Group A

Objective: assess the modern value of group А β-hemolytic streptococcus in patients with acute tonsillitis and the effectiveness of the rapid streptococcal antigen detection method.Materials and methods: microbial landscape assessment of acute tonsillitis was based on retrospective analysis of 902 bacterial culture results of a throat swab of patients with syndromes of acute tonsillitis treated in the Infectious Diseases Clinic of the Military Medical Academy named after S.M. Kirov during the period of 2019-2020. The effectiveness of the rapid streptococcal antigen detection method in the oropharynx was determined by a prospective study involving 35 patients with acute tonsillitis.Results: in the study, we have found that bacterial culture results of a throat swab, the following were more common: Nesseria species (39 %), Streptococcus viridans (23 %), and Staphylococcus aureus (17 %). The frequency of detection of β-hemolytic streptococcus was 1 %. The rapid diagnostic system «Streptatest» in patients with acute tonsillitis has demonstrated efficiency, under which that sensitivity of test was 80 %, specificity – 90 %, positive predictive value – 57,14 %, negative predictive value – 96,43 %.Conclusions: the frequency of group A β-hemolytic streptococcus in patients with lesion of lymphoid tissues of the oropharynx has declined significantly nowadays. The rapid diagnostic system «Streptatest» is a highly effective medical product that can be used in both hospital and pre-hospital stage.

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