Evaluation of clinical status according to the detected etiologic agent in children diagnosed with acute bronchiolitis in the pediatric emergency department

ABSTRACT Background and Aim: Acute bronchiolitis is a viral lower respiratory tract infection characterized by inflammation of the small airways, commonly seen in children under the age of two, particularly during the first year of life. It typically begins with upper respiratory tract symptoms such as nasal discharge and cough, followed by lower respiratory tract findings including tachypnea, wheezing, and retractions due to inflammation of the bronchioles. While respiratory syncytial virus (RSV) is the most frequent causative agent, other respiratory viruses such as rhinovirus, bocavirus, and coronavirus are also involved in the etiology. The clinical course can vary; in some cases, the disease may persist longer, requiring hospitalization, intensive care monitoring, or mechanical ventilation. In this study, we aimed to evaluate the relationship between the viral pathogen identified by respiratory viral panel (RVP) testing and clinical severity, treatment approach, and level of care (ward or intensive care unit) in pediatric patients diagnosed with acute bronchiolitis. Based on the collected data, we sought to clarify the role of viral agents in the clinical course and assess the contribution of RVP testing to patient management. Materials and Methods: This single-center, retrospective, observational study was conducted at the Pediatric Emergency Department and Level 2 Pediatric Intensive Care Unit of Ankara Bilkent City Hospital. Patients aged 1–24 months who were diagnosed with acute bronchiolitis and had a respiratory viral panel test with an identified viral pathogen between October 1, 2023, and April 30, 2024, were included. Demographic characteristics, clinical findings, laboratory and imaging results, and treatment approaches were compared based on the detected viral agents. Results: The study was conducted during the bronchiolitis season (October 2023 – April 2024) and included 414 pediatric patients (277 male, 66.9%; mean age 7.6 ± 6.3 months). Of all hospital admissions, 40.6% occurred in December. The most common presenting symptom was cough (95.4%), and the most frequent physical examination finding was tachypnea (93.5%). The most commonly detected viral agent was RSV A/B (42.5%), followed by rhinovirus (18.6%), SARS-CoV (10.1%), and bocavirus (8.2%). A total of 79.4% of patients were infected with one of these four viruses, and further analyses were performed within these groups. Most patients with RSV A/B bronchiolitis had a moderate disease course (77.3%). All patients with rhinovirus or bocavirus bronchiolitis had moderate or severe disease. In contrast, mild bronchiolitis was more frequently observed in SARS-CoV cases (9.5%). A statistically significant relationship was found between viral pathogen and clinical severity (p=0.047). ICU admission was more common in bocavirus (47.1%) and rhinovirus (32.5%) cases, with a significant association between viral pathogen and ICU requirement (p=0.032). Antibiotic use was highest in patients with bocavirus infection (70.6%) (p=0.038). Steroid treatment exceeded 70% in RSV A/B, rhinovirus, and bocavirus groups, while it was 57.1% in the SARS-CoV group (p=0.033). Neutrophilia was more common in rhinovirus (36.5%) and bocavirus (32.4%) infections (p<0.001), whereas leukopenia was more frequently observed in RSV (15.8%) and SARS-CoV (17.1%) infections (p=0.008). Nasal discharge was more prevalent in rhinovirus cases (p=0.014), and retractions were significantly more common in RSV A/B, rhinovirus, and bocavirus bronchiolitis (p<0.001). Wheezing was most frequently detected in rhinovirus cases (p=0.009). In addition, a history of recurrent lower respiratory tract infections was significantly more common in patients with rhinovirus bronchiolitis (54.5%) (p<0.001). Conclusion: Bronchiolitis is a common lower respiratory tract infection in infancy, especially during the winter months, most often caused by viral agents and typically requiring close clinical monitoring. Although the disease is self-limiting in the majority of cases, it may occasionally necessitate hospitalization, oxygen therapy, or even intensive care support. This variability in clinical course underscores the importance of evaluating both the viral pathogen and patient-specific factors in disease management. As demonstrated in this study, not only the type of virus but also comorbidities, environmental conditions, and individual risk profiles significantly influence disease severity. Therefore, while viral identification through RVP testing is valuable, treatment decisions should be based on a comprehensive clinical assessment. Moreover, reducing modifiable risk factors such as lack of breastfeeding, exposure to passive smoking, and household crowding is crucial for decreasing the incidence and severity of bronchiolitis. Integrating pathogen-based clinical insights with individualized, evidence-based treatment strategies may improve clinical outcomes and contribute to the efficient and sustainable use of healthcare resources. Keywords: Acute Bronchiolitis, Respiratory Viral Panel, PCR