Anaphylaxis%20(pediatric) Diagnosis
Diagnosis
Clinical Criteria for the Diagnosis of Anaphylaxis
- Diagnosis of anaphylaxis is highly likely when any 1 of the following 3 criteria is fulfilled:
- Acute onset of illness of minutes to several hours duration involving the skin, mucosal tissue, or both (eg pruritus, flushing, generalized hives, edema of lips, tongue and uvula)
- Plus at least 1 of the following:
- Respiratory compromise (eg dyspnea, stridor, bronchospasm, wheezing, hypoxia, decreased peak expiratory flow [PEF])
- Reduced BP or end-organ dysfunction symptoms (eg collapse, syncope, incontinence)
- ≥2 of the following that occur rapidly after exposure to a likely allergen of minutes to several hours duration
- Skin or mucosal tissue involvement (eg pruritus, flushing, generalized hives, edema of lips, tongue and uvula)
- Respiratory compromise (eg dyspnea, stridor, wheezing, bronchospasm, hypoxia, decreased peak expiratory flow)
- Reduced BP or associated symptoms (eg collapse, syncope, incontinence)
- Gastrointestinal symptoms that are persistent (eg crampy abdominal pain, vomiting)
- Decreased BP after exposure to known allergen of minutes to several hours duration
- Hypotension is defined as:
- SBP <60 mmHg for term neonates (0-28 days)
- SBP <70 mmHg for 1 month-1 years of age
- SBP < (70 mmHg + [2 x age]) for 1-10 years of age
- SBP <90 mmHg for 11-17 years of age
- >30% decrease in systolic BP
- Hypotension is defined as:
History
- A key part of the diagnostic work-up
- Important to identify risk and predisposing factors for possible recurrence (eg history of previous anaphylactic reactions, history of atopy, asthma even if well-controlled, adolescence, family history of any type of allergic reaction)
- Family history remains the most practical and useful tool in identifying allergy-prone infants
- Presence of allergic diseases in one or both parents and in a sibling increases likelihood of allergy in a child
- Determine and record the time of onset of symptoms and the circumstances prior to the reaction, including treatments given
- Obtain a detailed history of all the food and drugs taken, and all the patient’s activities, including history of sting or bite, over the 4-6 hours period prior to the episode
Laboratory Tests
- Given a reliable history, serum specific IgE, skin prick test and food patch test will confirm the diagnosis
- However, anaphylaxis may be seen in patients without cutaneous manifestations or specific IgE
- Skin prick and in vitro tests may help identify specific IgE antibodies reacting to the etiologic agent
- Food challenge is warranted in patients with a history of life-threatening anaphylaxis when the causative agent cannot be conclusively determined by history and laboratory exam, or if the patient is believed to have outgrown their food sensitivity
- May include exercise testing if exercise is considered an amplifying factor
- Testing serum tryptase level is not specific for anaphylaxis but can sometimes be useful to support the clinical diagnosis of anaphylaxis
- Acquire a sample right after starting emergency treatment
- Acquire a second sample within 1-2 hours (but no later than 4 hours) from onset of symptoms
- Measure baseline tryptase at least 24 hours after complete resolution of symptoms
- May be elevated for up to 12 hours in drug-induced and bee-sting anaphylaxis; however, serum elevation is also noted in systemic mastocytosis and hereditary alpha tryptasemia
- Rarely elevated in food anaphylaxis in children
- Degree of elevation is associated with the degree of hypotension
- Normal levels do not exclude diagnosis of anaphylaxis
- Acquire a sample right after starting emergency treatment
- Other tests to be considered include urinary 5-hydroxyindoleacetic acid, urinary methylhistamine, chromogranin A, vasointestinal polypeptide, oligosaccharide alpha-gal antibodies (for red meat hypersensitivity in persons with history of tick bites), and catecholamines