Allergy laboratory

Specific IgE measurement

Summary

Science

Clinical

Clinical

Allergy consultants may often use an exposure test to diagnose a patient with mild allergic symptoms. In some cases though, the risk of a causing a severe allergic response by performing this kind of test is considered too great, so an indirect laboratory approach is used instead. This may be the case if a patient has presented at and Accident and Emergency department with severe allergic symptoms. An acute allergic response affecting many parts of the body at once is called anaphylaxis and can lead to many symptoms including rashes, swelling of the airways, vomiting, itching, reduction in blood pressure and it can even result in death. The initial response here is to reduce the symptoms of anaphylaxis by giving the patient adrenaline and anti-histamines. After the patient’s condition has stabilised the doctors can begin to investigate exactly what caused the severe reaction. In this incident, the clinician in charge may suspect that something in the meal the patient recently ate lead to the anaphylaxis but because the reaction was so severe it would not be wise to expose the patient again in a skin prick test. The immunology laboratory would therefore be asked to perform a specific IgE quantification using the IMMUNOCAP technology. The patient’s serum would be tested first against a mixture of common food allergens including peanut, if this was positive, the patient could then be tested against each of the individual allergens. If the final result showed that the patient had elevated levels of IgE specific for peanut then the clinician would advise avoiding further exposure and also show them how to inject themselves with adrenaline using a device called an Epipen in case of accidental exposure.

• Science