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Sunday 24 March 2019
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Guideline for the management of nut allergy helps to define diagnostic pathways, including the role of specific IgE testing

 

A new guideline published by the Standards of Care Committee of the British Society for Allergy & Clinical Immunology (BSACI) aims to bring together the latest science in order to improve the diagnosis and management of peanut and tree nut allergy.1

Developed using NICE-accredited processes and following extensive consultations with allergy organisations and experts, the step-by-step guideline includes algorithms to support the use of both skin-prick testing and IgE testing. In particular, the guideline establishes the role of new molecular-based component-specific IgE testing as part of a comprehensive approach to diagnosis.    

Current diagnostic approaches to support clinical history taking include taking skin prick tests (SPT) and whole nut-specific serum IgE (sIgE) tests (directed at particular nuts under scrutiny such as whole tree nuts or whole peanuts, for example).   All these factors are important, but there are problems with using any of them alone as single indicator of a diagnosis (although for someone with a strong history of an immediate reaction to peanuts there is an 80% probability of a primary peanut allergy). Using peanut allergy as an example, while whole peanut specific serum IgE (sIgE) can be used to confirm sensitisation, measurements are not a reliable predictor of allergy. Even hospital-based challenges do not necessarily provide a good way of predicting how somebody might react in the future.

The new type of test recommended in the guideline is based on reactions to specific proteins within nuts. For peanut allergy, the new test measures IgE to Ara h 2, the most important primary peanut allergen. Sensitisation to Ara h 2 is detected in over 90% of people with a life-threatening peanut allergy2.  The ability to test for this allergen may significantly help to improve diagnosis of those at risk of severe reactions, and represents a major step forward.   

While the new test currently applies only to peanut allergies, there has also been work to identify two hazelnut components (Cor a 9 and Cor a 14) which could be of similar value. Similar component specific testing for other tree nuts is expected to follow soon.   

The introduction of this new nut allergy guideline is particularly timely given the continued increase in the numbers of people with allergies and a rise in deaths, particularly in younger patients, since the early 1990s. Today, nut allergies are a global problem that affect over two per cent of children and one in 200 adults. Often a lifelong condition requiring constant vigilance, nut allergy may reduce quality of life even more than illnesses such as diabetes.

The new guideline seeks to add context to decision making and give practical help to healthcare professionals, enabling them to identify and prioritise those patients most in need of diagnosis and support.

New and updated areas covered by the guideline also cover:

  • -       Identifying high risk groups of patients (e.g. young children with severe eczema or an egg allergy) and assessing siblings
  • -       The latest thinking on allergy management, particularly for children, focusing on how a systematic approach that involves all caregivers – including grandparents, nurseries and schools - rather than just immediate family can help minimise accidental exposure
  • -       Comprehensive management plans including avoidance advice and emergency treatment.
  • -       Making effective use of a range of specialists, including dietitians
  • -       A summary of latest thinking on key areas including:
  • o   New approaches to weaning that involve introducing peanut protein as part of the process – with the potential to reduce the numbers of adults with nut allergies in the future
  • o   Clinical trials of peanut oral immunotherapy

Dr Andrew Clark, a lead author of the new guideline, is excited about its scope, and believes it will be of real benefit to HCPs, including those in secondary care. ‘We wanted to combine practical advice with a summary of current thinking on a range of issues, from new tests to immunotherapy – something that was urgently needed given the extensive debate on all these areas,’ he says.

The full guidelines can be found at :

http://www.bsaci.org/Guidelines/peanut-and-tree-nut-allergy

References

1.    Stiefel G, Anagnostou K, Boyle RJ, et al. BSACI guideline for the diagnosis and management of peanut and tree nut allergy.  Clinical & Experimental Allergy 2017;47:719–739.

2.    Mueller, G. A. et al. Ara h 2: crystal structure and IgE binding distinguish two subpopulations of peanut allergic patients by epitope diversity. Allergy 2011;66:878–885.

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