Criteria for diagnosing anaphylaxis

Criteria for diagnosing anaphylaxis

The following diagnostic criteria are likely to capture more than 95% of cases of anaphylaxis2 and are described in Table 3.

Table 3. Clinical criteria for diagnosing anaphylaxis2

Anaphylaxis is highly likely when any one of the following 3 criteria is fulfilled:

Because the majority of anaphylactic reactions (>80%) include skin symptoms, it was judged that at least 80% of anaphylactic reactions should be identified by criterion 1 — even when the allergic status of the patient and potential cause of the reaction is unknown. However, cutaneous symptoms might be absent in up to 20% of anaphylactic reactions in children with food or insect sting allergy.

Criterion 1. Acute onset of an illness (minutes to several hours) with involvement of the skin, mucosal tissue, or both (eg, generalized hives, pruritus or flushing, swollen lips-tongue-uvula)

AND AT LEAST ONE OF THE FOLLOWING:

  1. Respiratory compromise (eg, dyspnea, wheeze-bronchospasm, stridor, reduced peak expiratory function [PEF], hypoxemia)
  2. Reduced blood pressure (BP) or associated symptoms of end-organ dysfunction (eg, hypotonia [collapse], syncope, incontinence)

In patients with a known allergic history and possible exposure, criterion 2 should provide ample evidence that an anaphylactic reaction is occurring.

Criterion 2. Two or more of the following that occur rapidly after exposure to a likely allergen for that patient (minutes to several hours):

  1. Involvement of the skin-mucosal tissue (eg, generalized hives, itch-flush, swollen lips-tongue-uvula)
  2. Respiratory compromise (eg, dyspnea, wheeze-bronchospasm, stridor, reduced PEF, hypoxemia)
  3. Reduced BP or associated symptoms (eg, hypotonia [collapse], syncope, incontinence)
  4. Persistent GI symptoms (eg, cramping abdominal pain, vomiting)

Criterion 3 should identify the rare patients who experience an acute hypotensive episode after exposure to a known allergen.

Criterion 3. Reduced BP after exposure to known allergen for that patient (minutes to several hours):

  1. Infants and children: low systolic BP* (age specific) or greater than 30% decrease in systolic BP
  2. Adults: systolic BP of less than 90 mm Hg or greater than 30% decrease from that person’s baseline

* Low systolic BP for children is defined as <70 mm Hg from 1 month to 1 year; < (70 mm Hg + [2 X age]) from 1 to 10 years; and <90 mm Hg from 11 to 17 years

Adapted from Sampson et al, J Allergy Clin Immunol, 2006.