Retrospective study of group A Streptococcus oropharyngeal infection diagnosis using a rapid antigenic detection test in a paediatric population from the central region of Portugal.

Group A Streptococcus (GAS) is one of the most important agents of oropharyngeal infection. To avoid unnecessary antibiotic prescription, it is recommended the confirmation of GAS infection in pharyngeal swabs using culture or rapid antigen detection test (RADT). This study aimed to retrospectively analyse the incidence of GAS oropharyngeal infection, detected by RADT, in a paediatric population in the Centre of Portugal. Data was collected from the database of the Paediatric Hospital Emergency Department (ED) regarding patients admitted with symptoms suggesting acute pharyngitis, from January 2013 to December 2018, in a total of 18,304 cases. Among these, 130 clinical files were searched for symptoms, complications and additional visits to the ED. The results showed an average GAS infection prevalence of 33%, with seasonal variation. In preschool children, especially in patients less than 3 years old, where the guidelines do not routinely encourage RADT, GAS tonsillitis assumed an unexpected importance, with 731 positive tests in a total of 3128 cases. Scarlatiniform rash and oral cavity petechiae had significant correlation with streptococcal aetiology (p < 0.05). The statistical analysis also showed that different signs and symptoms assume different weights depending on the age group of the patient. The main conclusion is that the incidence of GAS infection in the studied population is higher than generally described in preschool children, suggesting the need for a more cautious approach to children under 3 years presenting acute pharyngitis, and that RADT in this age group would contribute to a decrease in the number of unnoticed cases.