Anaphylaxis: skin prick tests and IgE levels were commonly abnormal

Clinical bottom line (level 4)

Half of patients with anaphylaxis had atopy and a sixth had a previous episode.
Two-thirds of patients with anaphylaxis had abnormal skin prick tests or allergen-specific IgE levels. Few other tests were helpful.

Yocum and Khan: Mayo Clinic Proceedings 1994; 69: 16-23

Expires November 2004

The study

Case series with unblinded, unobjective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: university hospital, USA

179 patients (aged mean 36, 66% female) with anaphylaxis (respiratory or cardiovascular symptoms and generalised pruritis, urticaria, angioedema or flushing)
Patients underwent

skin prick testing
blood tests: allergen-specific IgE antibody levels, C1-esterase inhibitor, serum complement, cryoglobulin levels, tryptase assays
urine tests: 5-hydroxyindoleacetic acid, methylimidazoleacetic acid and histamine
oral challenges with dye, metabisulfite and aspirin

Outcomes studied:

abnormal skin test or allergen-specific IgE
history of atopy
previous anaphylaxis
food
idiopathic
insect sting
medication
exercise

The evidence

outcome	time to outcome	number of patients/total number	% (95% CI)
abnormal skin test or allergen-specific IgE	?	123/179	69% (62% to 76%)
history of atopy	?	88/179	49% (42% to 56%)
previous anaphylaxis	?	32/179	18% (12% to 24%)
food	?	59/179	33% (26% to 40%)
idiopathic	?	34/179	19% (13% to 25%)
insect sting	?	25/179	14% (8.9% to 19%)
medication	?	23/179	13% (7.9% to 18%)
exercise	?	12/179	6.7% (3.0% to 10%)

Comments

No patient had abnormal blood tests (except IgE), urine tests or oral challenge tests.

Citation

Yocum MW, and Khan DA: assessment of patients who have experienced anaphylaxis: a 3-year survey. Mayo Clinic Proceedings 1994; 69: 16-23

_{Clinical Question.}

_Patient	_{suspected anaphylaxis}
_{Intervention or Exposure}	_{serum IgE}
_Outcome	_{confimed anaphylaxis, prevelance}