Tests
1st tests to order
clinical diagnosis
Test
Any suspicion of anaphylaxis should prompt immediate action.
Little, if any, formal testing is helpful in acute encounters; often definitive diagnosis is not achievable acutely.
History is the primary diagnostic tool in patients with a past history of allergic reaction to a sting.
Result
diagnosis is almost always based on history, physical exam, and clinical judgment
Tests to consider
serum tryptase
Test
In all cases of sting anaphylaxis, drawing blood to obtain tryptase levels within 1-5 hours of onset of symptoms (ideally within 1-2 hours) can verify that mast cells were activated and may help establish a diagnosis of anaphylaxis.
Elevated baseline serum tryptase is closely correlated with the risk of severe anaphylaxis to insect stings, and checking baseline serum tryptase at a later date is recommended for individuals with a prior history of severe anaphylaxis from Hymenoptera stings particularly in those who present with a history of hypotension and/or absence of urticaria as these may be indicators of an underlying mast cell disorder.[3][5][32][38]
Result
normal or elevated
sensitivity testing
Test
Sensitivity testing, including venom skin tests or in vitro serologic tests, are indicated in individuals who have suffered sting-triggered anaphylaxis to determine what venom allergen they are sensitized to and to inform their immunotherapy treatment prescription.[19][32][39]
This should not be done in the acute setting, as depletion of mediators from the reaction may result in a false-negative response. Skin testing should be delayed for 2-6 weeks after the acute event.
Due to the high rate of asymptomatic sensitization (i.e., evidence of venom-specific IgE without a correlating clinical history of venom allergy) in the general population (up to 20% of adults), generalized screening is impractical and not recommended.[15][32][40][41]
Result
quantifiable response to specific antigen
CBC
Test
Cellulitis or infected bites/stings will cause elevation of WBC levels.
Result
normal or elevated WBC
Use of this content is subject to our disclaimer