SHARED Study (Saguenay Hospitals Anaphylaxis Rule for Early Discharge) (SHARED)

  • End date
    May 3, 2023
  • participants needed
  • sponsor
    Université de Sherbrooke
Updated on 30 May 2022


Anaphylaxis is a potentially fatal condition with a prevalence between 0.05 and 2% in the general population. This is therefore a frequent reason for emergency visits. Its diagnosis is mainly based on the NIAID / FAAN2 criteria, developed in 2006. The treatment of the condition consists of administration of intramuscular (or intravenous) epinephrine and the hemodynamic support of the patient, if necessary. Various other agents are frequently administered (class I and II antihistamines, corticosteroids) but their role is recognized to be less central than that of epinephrine. The relevance of corticosteroids in reducing the risk of rebound reaction is even questioned.

After anaphylaxis, a serious phenomenon called a "biphasic reaction" can occur. This reaction is the return of symptoms of anaphylaxis resolution of the initial episode. The theoretical risk of a rebound reaction, or biphasic reaction, is conventionally described up to 72 hours after the initial anaphylactic event. Biphasic reaction is defined as a recurrence or occurrence of new signs or symptoms after resolution of the initial reaction, without re-exposure to the allergen. The potential occurrence of a biphasic reaction often warrants observation of patients for several hours in emergency departments following management of the initial anaphylaxis. Although recommendations and guidelines generally suggest observation times of four to six hours, there is no clear consensus or convincing evidence to guide this conduct. It sometimes even is suggested to observe patients for up to 24 hours.

Problem: To date, there are no prognostic factors to identify a patient at greater risk who would benefit from such an observation. As these reactions are a relatively rare phenomenon (i.e. 4 to 5%, but which could go up to 20% according to some sources and the symptoms observed are usually less significant than during the initial presentation, it is therefore possible that a prolonged observation period may not be necessary for some patients who do not have high risk factors for biphasic reaction. In the current context of the growing number of people in emergency rooms and limited ressources, it seems essential to identify low risk patients in order to discharge them quicker and safely by limiting unnecessary observation periods.

Objective: Identify and evaluate in a prospective manner previously derived (literature review and preliminary rules derivation already completed) clinical decision rules that are simple, generalizable and valid which could therefore become an interesting assets for the modern practice of emergency medicine as regards to post anaphylaxis rebound reaction risk stratification. It appears likely that some patients who have suffered an anaphylactic reaction could be safely discharged much earlier than in current practices. The rules would give clear guidelines to clinicians especially those working in lower flow settings, where clinical experience with the disease is less developed. Ultimately, these rules would also be relevant for teaching purposes for the various learners who do internships in emergency rooms.


This study is part of an ongoing projet to create, derive and validate a clinical decision rule with regards to the stratification of the biphasic reaction risk following an anaphylaxis event that has mandated an emergency room visit.

Phase 0: Systematic literature review (completed)

Phase 1: Statistical derivation of two clinical decision rules (retrospective observational study) - (completed)

Phase 2: Validation of clinical decision rules (prospective observational study - theoretical) - (underway)

Objective: The objective of phase 2 will then be to test the applicability and performance of our clinical decision rules in a prospective observational manner.

Methods: Based on the three clinical decision rules (2 derived from phase 1and one based on the literature review), a prospective observational study will be carried out in the emergency rooms of Chicoutimi, Jonquière and Alma. Data collection for this theoretical validation phase has been underway since December 2019, having received the approval of the various local research committees (ethics, science and convenience).

A questionnaire was developed from the three rules derived in the previous phases. All the elements present in these rules have been grouped by categories (history, allergen, symptoms and treatment). In this way, the criteria for each rule were not placed one after the other so that no rule could be recognized or inferred. This questionnaire was presented during department meetings. It is placed on the charts of patients with suspected anaphylaxis at triage and also is available at strategic locations in all three emergency rooms (for example, in the reanimation room).

Doctors are therefore invited to complete the questionnaire anonymously following their initial management of an anaphylactic reaction. Thereafter, they treat the patient as they would have done according to their usual practice. No rules is applied to the patients and the answers provided have no impact on their future care. The questionnaires are then deposited in a secured location determined for this purpose, in each of the emergencies.

The collection of files began in December 2019 and is still ongoing. The inclusion and exclusion criteria were the same as in phase 1. However, a patient who did not yet meet the criteria for anaphylaxis, but who, according to the clinician's assessment, would inevitably progress to an anaphylactic reaction could also be included if treated in this way. This is then clearly indicated on the questionnaire.

At the end of the preliminary recruitment period, all completed questionnaire files will be reviewed to determine if a biphasic reaction has occurred. The three clinical decision rules will then be applied to the population to test their performance, validity and safety.

It will also be of interest to assess the number of patients who could have been safely discharged without an observation period if each of the rules had hypothetically been applied. This analysis will also be carried out.

Lastly, the investigators propose to run a phase 3 trial, if the phase 2 trial identifies valid and clinically usable clinical decision rule(s). That phase 3 trial will aim to prospectively validate in real clinical setting and in a different patient population subset the selected rule(s).

Condition Anaphylaxis, Biphasic Anaphylactic Reaction, Rebound Anaphylactic Reaction
Treatment Occurence of biphasic reaction following anaphylaxis
Clinical Study IdentifierNCT04755881
SponsorUniversité de Sherbrooke
Last Modified on30 May 2022


Yes No Not Sure

Inclusion Criteria

Patients of all ages with anaphylaxis (meeting the NIAID/FAAN criteria)
Patients of all ages considered to be inevitably evolving torwards overt anaphylaxis by the threading physician

Exclusion Criteria

Adverse reaction to a medication (eg ACEI)
Hereditary angioedema
Known immune mediated Angioedema
Anaphylactoid reaction
Clear my responses

How to participate?

Step 1 Connect with a study center
What happens next?
  • You can expect the study team to contact you via email or phone in the next few days.
  • Sign up as volunteer  to help accelerate the development of new treatments and to get notified about similar trials.

You are contacting

Investigator Avatar

Primary Contact


Additional screening procedures may be conducted by the study team before you can be confirmed eligible to participate.

Learn more

If you are confirmed eligible after full screening, you will be required to understand and sign the informed consent if you decide to enroll in the study. Once enrolled you may be asked to make scheduled visits over a period of time.

Learn more

Complete your scheduled study participation activities and then you are done. You may receive summary of study results if provided by the sponsor.

Learn more

Similar trials to consider


Not finding what you're looking for?

Every year hundreds of thousands of volunteers step forward to participate in research. Sign up as a volunteer and receive email notifications when clinical trials are posted in the medical category of interest to you.

Sign up as volunteer

user name

Added by • 



Reply by • Private

Lorem ipsum dolor sit amet consectetur, adipisicing elit. Ipsa vel nobis alias. Quae eveniet velit voluptate quo doloribus maxime et dicta in sequi, corporis quod. Ea, dolor eius? Dolore, vel!

  The passcode will expire in None.

No annotations made yet

Add a private note
  • abc Select a piece of text from the left.
  • Add notes visible only to you.
  • Send it to people through a passcode protected link.
Add a private note