Ige, specific

Suspected IgE-mediated immediate type reaction, proof of sensitization. Impossible to perform skin tests in case of reaction anomalies of the skin (e.g. urticaria factitia, atopic dermatitis, etc.).

Immunoassay, competitive or immunometric method using an enzyme, fluorescence, luminescence or radioactively labeled reaction partner in the antigen-antibody reaction.

Specific IgE (sIgE) is determined in serum, whereby only circulating sIgE is detected. Cellular sIgE, however, is not. The patient's serum is incubated on an allergen-containing matrix, after which the sIgE is quantified, for example using a fluorescent antibody (fluorescent enzyme immunoassay - (FEIA).

Other methods are:

• EAST: Enzyme Allergo Sorbent Test (EAST) in which specific IgE is detected with the help of enzyme conjugates.
• RAST: These non-radioactive methods have largely replaced radioactive methods such as the radio-allergo sorbent test (RAST). However, the term RAST is still often used in everyday life for the detection of specific IgE.
• The determination of drug-specific IgE is typically carried out in cases of suspected IgE-mediated immediate type reactions. However, validated commercial tests are only available for a small number of drugs (mainly beta-lactams) (sesnitivity: 80-85%, specificity > 50%).

Test material = serum (1-2 ml). Recently, there have been approaches to determine the antibodies from nasal secretions, as it has been shown that there is a direct correlation between IgE levels in the blood and those in nasal secretions for a wide range of allergens (Gökkaya M et al. 2020).

1. Gökkaya M et al (2020) Nasal specific IgE correlates to serum specific IgE: First steps towards nasal molecular allergy diagnostic. Allergy 75:1802-1805.

2. Renz H et al (2009) In vitro allergy diagnostics. Guideline of the German Society for Allergology and Clinical Immunology (DGAKI) Allergo J 19: 110-128