In this section
March 2025
There are a few ways for assessing patients for allergy, one of which is performing specific IgE blood testing. Specific IgE blood testing is like the former blood “RAST” testing for allergies. The Royal College of Pathologists has recently published Best Practice Recommendations (BPR) for allergy testing (see the section “Immunology and allergy”). This guide outlines the characteristics of allergies and indicates when allergy testing is necessary.
Specific IgE testing is only indicated in assessing patients for immediate hypersensitivity reactions to a specific allergen. The ‘STAR’ framework below describes the main features of an immediate IgE mediated hypersensitivity reaction.
- Symptoms: Are Symptoms in keeping with IgE mediated mechanism?
- Timing: Is the Timing in keeping with an IgE mediated mechanism?
- Allergen: Can the symptoms be attributable to a likely Allergen?
- Reproducible: Are the symptoms Reproducible with every exposure to the allergen?
Below is a summary of the main recommendations in the RCPath BPR:
- Specific IgE testing should only be performed if all ‘STAR’ features are present
- The features of allergy include an urticarial rash, angioedema, wheeze, vomiting, diarrhoea and hypotension
- Isolated gastro-intestinal symptoms are generally not in keeping with IgE mediated reaction and therefore specific IgE testing should not be performed for isolated GI symptoms
- Testing should be limited to the specific trigger that the patient was exposed to within 1 hour of the reaction onset
- Specific IgE testing to food mixes are not helpful in assessing food allergy as they do not inform which allergen the patient is allergic to
- Foods that have been tolerated and consumed after the reaction do not require any testing
- Not all patients with rhinitis symptoms require specific IgE testing to aeroallergens; it is only recommended in primary care where it will affect patient management (e.g. checking for cat specific IgE if this will result in avoidance) or if it is required prior to referral to specialist services. For rhinitis symptoms that are present all year round, consider testing house dust mite or animal dander. Seasonal rhinitis is mainly caused by pollens; refer to the Allergy UK infographic calendar to identify the likely allergens.
- Drug specific IgE should not be performed in primary care, instead refer to the NICE guidance on drug allergy.
- Specific IgE to venom should only be performed when there have been immediate systemic reactions to bee or wasp stings. Patients with immediate systemic reactions to venom should be referred to allergy/immunology services and a baseline mast cell tryptase, in addition to the specific IgE to bee and / or wasp venom can be performed at the point of referral
- For referrals to allergy and immunology services, ‘STAR’ information should be included in the referral information, in addition to ‘ETRM’; Examination (cutaneous features, blood pressure, oxygen saturations, pulse rate), Treatment, Response to treatment, and Mast cell tryptase when this information is available
- Allergy testing is not indicated for chronic spontaneous urticaria/angioedema. This includes randomly occurring urticaria without a consistent trigger.
Changes to the specific IgE requesting process within Primary Care
Following these recommendations, the ICE page for requesting specific IgE blood tests in primary care at MFT has been updated. Previously, there were several specific IgE requests available on the home page. Now, only aeroallergens are visible on the page, as shown below on a test patient.
The new allergy request page
Other allergens can still be requested but will need to be searched and requested on an individual basis. For these requests a ‘pop-up’ will appear with the link to the RCPath BPR, as demonstrated below. To ensure testing to the allergen is appropriate, it is encouraged to review the guidance before requesting the specific IgE.
Pop-up with specific IgE requests with a link directing to the BPR guidelines
Thank you for assisting us with the implementation of the RCPath BPR within your practice. If you have any queries, please contact the Immunology laboratory team at MFT.