The measurement of allergen-specific immunoglobulin E (sIgE) is performed by fluorescent enzyme immunoassay, using allergen bound to a solid phase. It is important that allergy testing is guided by the clinical history. Random testing or ‘screening’ for IgE to irrelevant allergens is generally unhelpful and wasteful.

In the clinical history, consider whether the symptoms are appropriate to a diagnosis of allergy, and whether the time-course of the symptoms relative to exposure is in keeping with an IgE-mediated (immediate-type) reaction. For example, in food allergy, symptom onset is usually within an hour of exposure.

IgE tests are not absolutely predictive - a positive result does not necessarily mean that a patient is allergic, and a negative result does not necessarily exclude allergy. When requesting allergen-specific IgE levels, it is strongly recommended that the total IgE should also be requested, as this aids interpretation of the results. In particular, elevated allergen-specific IgE levels of no diagnostic relevance are commonly seen in patients with atopic eczema and a very high total IgE values.

Results should always be interpreted in the context of the clinical history.

For inhalant allergens, the aeroallergen panel may be requested. This includes cat, dog, house dust mite, tree pollens and grass pollens. This panel also includes total IgE. In all other circumstances, it is important to specify which allergen(s) you are interested in exploring, according to the clinical history.

Note that chronic urticaria (with or without angioedema) is typically non-allergic - requesting IgE tests to investigate frequent, apparently spontaneous, symptoms is generally unhelpful and unnecessary.

References:
Powell, R.J., et al. BSACI guideline for the management of chronic urticaria and angioedema. Clinical & Experimental Allergy, 45: 547-565

Stiefel, g. et al. (2017) BSACI guideline for the diagnosis and management of peanut and tree nut allergy. Clinical & Experimental Allergy, 47: 719-739

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