Adenoviral Pharyngitis in the Paediatric Emergency Department: The Pivotal Role of Rapid Antigenic Testing

<b>Background:</b> adenoviruses (AdVs) are DNA viruses that typically cause mild infections in immunocompetent children, and typically involve the respiratory and gastrointestinal tract. Adenoviral pharyngitis is a common paediatric illness, particularly in children under 4 years old. The aim of our 7-year retrospective study, conducted at a tertiary care paediatric emergency department (ED), was to describe the clinical and laboratory characteristics and management of patients with pharyngeal AdV infections. Specifically, we examined how the management of patients with adenoviral pharyngitis has evolved following the introduction of a rapid antigen nasopharyngeal swab test for AdVs, which has been performed directly in the ED since 2023. <b>Methods:</b> in this single-centre retrospective observational study, the demographic and clinical information for children discharged from the ED who had been diagnosed with a pharyngeal AdV infection between 1 January 2017 and 31 December 2023 were retrospectively reviewed. Moreover, we compared data before and after the introduction of rapid AdV antigenic swabs, which have been directly performed in the ED since the beginning of 2023. Statistical analysis was undertaken using the Student's <i>t</i>-test and Pearson and Fisher's exact test, as appropriate. Significance was set at <i>p</i>-value < 0.05. <b>Results</b>: during the study period, 172 children were diagnosed with adenoviral pharyngitis based on a positive swab. All patients were febrile, with a median duration of fever of 4 days. Blood tests were requested for 84.9% of patients at admission, resulting in a mean WBC count of 13,250/mmc and a mean CRP of 70.6 mg/L. The highest CRP median values were found on the third day of fever. Out of 383 swabs performed during 2017-2022, 13.6% were positive vs a 32% positive rate for the 372 swabs performed in 2023. The mean duration of observation in the ED before 2023 was 31.4 h vs. 10.4 h in 2023. Similarly, 9% of patients with adenoviral pharyngitis were admitted to a paediatric ward before 2023 and only 0.8% in 2023. <b>Conclusions:</b> the primary reason for ED admission in cases of adenoviral pharyngitis is fever lasting several days due to hyperinflammation. Differential diagnosis with bacterial infection is essential to limit the number of hospitalisations and inappropriate antibiotic therapy. The introduction of the rapid antigen nasopharyngeal swab has simplified the diagnosis of adenoviral pharyngitis, enabling timely and accurate differentiation from bacterial causes.