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