Biomarker: I070-IgE Fire Ant (Invicta)

Overview

I070-IgE Fire Ant (Invicta) measures immunoglobulin E (IgE) antibodies directed against allergens from the red imported fire ant, Solenopsis invicta. IgE is involved in immediate hypersensitivity reactions, including urticaria, angioedema, respiratory symptoms, and anaphylaxis after a sting. A detectable or elevated result indicates sensitization, but the concentration does not reliably predict the severity of a future reaction and must be interpreted with the clinical history. The test is clinically useful as an adjunct to evaluating suspected systemic fire-ant sting allergy and may help identify patients for specialist assessment and consideration of fire-ant immunotherapy.

Clinical Use Cases

Evaluate suspected IgE-mediated allergy after a systemic reaction to a red imported fire-ant sting.
Support assessment of patients with a history of anaphylaxis or other generalized symptoms after fire-ant exposure.
Provide an alternative or complementary test when skin testing is unsuitable, unavailable, or inconclusive.
Support referral to an allergist for consideration of imported fire-ant whole-body-extract immunotherapy when the clinical history and testing are consistent.
Complement, rather than replace, clinical history and physical assessment; testing is not recommended as a stand-alone screening test for asymptomatic individuals.

Specimen Types

Venous blood, generally processed as serum.
Plasma may be accepted by some assay systems, according to the performing laboratory’s validated requirements.

Measurement Methods

In-vitro allergen-specific IgE immunoassay using Solenopsis invicta fire-ant allergen extract.
Radioallergosorbent test (RAST), an older specific-IgE method.
Fluorescence enzyme immunoassay or other automated solid-phase immunoassays used by contemporary clinical laboratories.
Skin-prick or intradermal testing with imported fire-ant whole-body extract is an in-vivo complementary method, not a measurement of serum I070-IgE.
Results are commonly reported in kUA/L or equivalent assay-specific units with a laboratory-defined class or reference interpretation.

Test Preparation and Influencing Factors

Fasting is generally not required for a serum-specific-IgE blood test.
No special preparation is usually required, but the patient should report all prescription medicines, over-the-counter medicines, and supplements.
Antihistamines generally do not alter the antibody concentration measured by serum-specific-IgE testing, although they can interfere with skin testing. Medication changes should only be made at the direction of a healthcare professional.
Testing should be interpreted in relation to the timing, severity, and features of the sting reaction and the likelihood that S. invicta was the offending insect.
Specific IgE can be low or undetectable shortly after a sting. If clinical suspicion remains high after an initially negative result, repeat serum testing and/or skin testing may be considered after several weeks under specialist guidance.
A positive result indicates sensitization and does not by itself establish clinical allergy or predict reaction severity.
Cross-sensitization among some Hymenoptera venoms may complicate interpretation, so results should be evaluated alongside testing for other suspected insects when clinically appropriate.