ISTANBUL — A newly developed clinical prediction tool may help clinicians individualize observation periods for children presenting to emergency departments with anaphylaxis, potentially reducing unnecessary monitoring while identifying those at highest risk for recurrence.

The Pediatric Risk Evaluation for Predicting Anaphylaxis Recurrence in Emergency Department (PREPARED) score accurately stratified children according to their risk for biphasic anaphylactic reactions and could safely reduce prolonged observation in the emergency department for nearly three quarters of pediatric patients, investigators reported at the European Academy of Allergy and Clinical Immunology (EAACI) 2026 Annual Congress.

“The main gap in anaphylaxis care is how long to observe a patient,” said Waleed Alqurashi, MD, pediatric emergency physician at the Children’s Hospital of Eastern Ontario Research Institute and associate professor at the University of Ottawa in Ottawa, Ontario, Canada. “Current practice varies widely between early discharge, which may be unsafe for some patients, and prolonged observation, which consumes healthcare resources unnecessarily,” he said.

Addressing a Long-Standing Clinical Dilemma

Biphasic reactions, which comprise the recurrence of anaphylactic symptoms after initial resolution without reexposure to the trigger, occur in approximately 5%-15% of children with anaphylaxis. Current recommendations regarding the duration of post-anaphylaxis observation vary substantially and are based on limited evidence.

To address this uncertainty, Alqurashi and his colleagues conducted a prospective multi-center cohort study across seven pediatric emergency departments within the Pediatric Emergency Research Canada network between 2022 and 2025. The study enrolled 1686 children younger than 18 years who met the World Allergy Organization diagnostic criteria for anaphylaxis. Patients were monitored during their emergency visit and followed up 2-5 days after discharge to identify delayed biphasic reactions.

The primary outcome was an anaphylactic biphasic reaction with an asymptomatic interval of at least 1 hour.

1 in 8 Children Experienced a Reaction

Among the children in the study, 225 (13.3%) experienced a biphasic reaction of any kind. Of these, 115 cases (51.1%) met criteria for anaphylactic biphasic reactions, according to the researchers. Notably, 53 of the 115 anaphylactic biphasic reactions (46%) occurred after discharge from the emergency department, and 35 of those children (66%) subsequently returned to the unit.

Using regression analysis, Alqurashi’s group identified eight predictors of anaphylactic biphasic reactions: age, female sex, concurrent active asthma, unknown trigger, cardiovascular signs, respiratory signs, gastrointestinal symptoms, and requirement for two or more doses of adrenaline.

The resulting PREPARED score ranges from 0 to 15 points, and risk stratification identified four distinct groups. Children in the very-low-risk group (0-2 points), comprising 26% of patients, had a 2.5% risk for biphasic anaphylaxis. The low-risk group (3-5 points), which included 47% of patients, had a 6.1% risk. Among the medium-risk group (6-9 points), representing 25% of patients, the risk increased to 10.9%. Children in the high-risk group (10 or more points) accounted for 2% of the cohort but had a 27% risk of experiencing a biphasic reaction. Although the score was not perfectly predictive, analyses suggested it could help clinicians balance the risks for early discharge against unnecessary prolonged observation, the researchers said.

Observation Times Tailored to Risk

Based on the score, investigators proposed observation periods that increase according to risk level. Children in the very-low-risk group could potentially be discharged approximately 1 hour after resolution of symptoms, whereas low-risk patients might require 2-3 hours of observation and medium-risk patients 4-5 hours. High-risk patients may warrant hospital admission and observation for at least 20 hours.

Alqurashi emphasized that the recommendations are intended to support shared decision-making rather than replace clinical judgment. Importantly, the score could challenge current fixed observation practices. “We proposed decision recommendations that are based on shared decision-making and balancing safety and care,” he said.

Surprising Finding on Initial Severity

One unexpected finding was that severe symptoms occurring before arrival at the emergency department did not predict subsequent biphasic reactions if the child was clinically stable when assessed there. “Even if they had severe respiratory distress or they had low blood pressure before arriving in the emergency department, if they arrive at the emergency department and they’re fine, they’re going to be fine,” Alqurashi said.

The finding suggests that a patient’s clinical status at assessment may be more informative than the severity of symptoms experienced before arrival at the emergency department, he added.

Unknown Triggers Linked to Higher Risk

Another important predictor was an unknown trigger. During the discussion session, a delegate noted that “unknown triggers emerged as an independent predictor of biphasic anaphylaxis in the PREPARED score. Why might an unidentified trigger increase the risk for a secondary reaction, and what implications might this finding have for post-discharge allergy investigation and follow-up?”

Alqurashi said the finding was consistent with previous research showing patients with an unknown trigger are at greater risk for biphasic reactions. These patients may present later for medical attention because they do not initially recognize what has caused their symptoms, he said, potentially leading to delays in diagnosis and treatment.

“Clinicians don’t know what to do with them sometimes because they don’t know what they’ve reacted to,” he said. “That’s part of the reason why those patients end up with delayed presentation and delayed treatment,” which may contribute to an increased risk for severe or delayed recurrent reactions.

Approximately 70% of initially unidentified triggers in the study group were eventually determined during follow-up, he said.

The investigators estimate that implementation of the PREPARED score could reduce unnecessary observation for nearly 75% of children presenting with anaphylaxis while maintaining patient safety.

The high-risk group represented about 2% of patients, suggesting that increased admissions would be limited. In fact, Alqurashi noted that current admission rates may decrease if the score is adopted. The next step will be external validation of the model in independent populations.

“The PREPARED score addresses an important clinical gap by moving beyond arbitrary, fixed observation periods towards a more individualized, risk-based approach to monitoring children with anaphylaxis,” said I-Jen Wang, MD, PhD, director of the Department of Allergy and Immunology Medicine at Taipei Hospital in New Taipei City, Taiwan.

“However, the model demonstrated only moderate discrimination, and the study was conducted within a single research network,” Wang said. “External validation in other healthcare settings will therefore be essential before the score can be widely adopted.”

Graham Roberts, DM, professor of pediatric allergy and respiratory medicine at the University of Southampton in Southampton, England, praised the size of the study and its generation of “lots of data.” However, he observed that the rate of biphasic anaphylaxis was higher than in most previous studies. “The authors’ score to predict biphasic anaphylaxis is interesting and would be very helpful to emergency department staff,” Roberts said. “At this stage, though, it should be considered to be preliminary, as it needs to be validated in another study, preferably in different locations.”

The study was supported by Pediatric Emergency Research Canada and Food Allergy Canada. Alqurashi reported research funding related to the study and disclosed no other relevant conflicts of interest during the presentation. Roberts and Wang reported no relevant financial conflicts of interest.