Observation Periods and Biphasic Reaction Risk Factors in Pediatric Emergency Anaphylaxis Cases

Anaphylaxis is a severe, potentially life-threatening systemic hypersensitivity reaction with rapid onset. Its incidence in children has been rising worldwide. Although international recommendations emphasize the importance of post-reaction monitoring, the optimal observation period in pediatric patients remains uncertain, largely due to the risk of biphasic reactions, defined as recurrence of symptoms after initial resolution within 1-72 hours.

This retrospective observational study was conducted in the Pediatric Emergency Department of Adnan Menderes University Hospital. All patients younger than 18 years who presented with anaphylaxis between January 1, 2014, and December 31, 2024, were included. Diagnosis was based on the World Allergy Organization (WAO) 2020 criteria. Data were obtained from electronic medical records and emergency department charts.

Collected variables included demographics (age, sex), season of presentation, suspected triggers (food, drug, insect sting, exercise, idiopathic), clinical manifestations (cutaneous, respiratory, cardiovascular, gastrointestinal, neurological), comorbidities (such as asthma), acute treatments (epinephrine administration, time to first dose, number of doses, corticosteroids, antihistamines, fluid therapy), observation duration, need for hospital admission, and occurrence of biphasic reactions.

The primary objective is to determine the incidence and timing of biphasic reactions. Secondary objectives are to assess the average observation period in the emergency department, the frequency of hospital admission, and risk factors associated with biphasic reactions, including delayed epinephrine administration and history of asthma. Statistical analysis will include descriptive methods, group comparisons, and logistic regression to identify independent predictors of biphasic reactions.

This study is expected to contribute real-world data on pediatric anaphylaxis and inform clinical practice regarding safe observation times. Results will be compared with existing evidence and may support improvements in pediatric emergency protocols for anaphylaxis management.

Inclusion criteria

Age <18 years

• Diagnosis of anaphylaxis according to World Allergy Organization (WAO) 2020 criteria
• Complete clinical data available in medical records

Exclusion criteria

• Incomplete or missing clinical data
• Cases not meeting WAO 2020 anaphylaxis definition
• Patients presenting with isolated urticaria or localized allergic reactions only