Lower limit of in vitro clinically significant venom IgE
Question:
5/9/2017
33 y/o African American male presents with history of venom anaphylaxis at age 4. He states stopped breathing when he stepped on a bee at age 4. He does not recall the reaction, the history was given to him by his mother. His skin testing for venoms was negative. RAST testing shows IGE levels for wasp 0.14, white hornet .57, yellow hornet .20, yellow jacket .14, honeybee <.10. Does this patient need treated with venom immunotherapy?
Answer:
There is no clear answer. The Stinging Insect Hypersensitivity Practice Parameter (2016) notes "Ten percent of patients with skin test negative responses have positive in vitro test results when using assays capable of detecting low level venom specific IgE antibodies. Although technical improvements permit reporting of serum levels between 0.1 and 0.35 kU/L, the clinical significance of these low levels has not been determined. Very low levels of venom IgE could be clinically significant, particularly in the context of relatively low total serum IgE." Based on the reaction when the patient was 4 years old you could consider measuring a serum tryptase to screen for a mast cell disorder.
We hope this helps.
Patricia McNally, MD, FAAAAI