New blood test to help manage severe allergic reactions

 Southampton researchers have developed a pioneering test that indicates which people are most at risk from life-threatening allergic reactions.

The innovative test, which measures levels of an enzyme in the blood that is involved in allergic reactions, was developed by the University of Southampton's Dr Andrew Walls working with doctors at Southampton General Hospital. It could become the gold standard test for the diagnosis of severe allergic reactions across the world.

"Allergic reactions to drugs are increasingly common and reactions to food such as peanuts, tree nuts and fruit are also a concern, particularly in children and adolescents," said Dr Walls, reader in immunopharmacology.

"But reliable tests for establishing the risk of a reaction have not been available, leaving patients vulnerable to serious reactions in the future."

Levels of an enzyme called CPA3 are considerably higher in the blood of people who are prone to life-threatening allergic reactions compared to those who are not.  The level of enzyme can increase rapidly within minutes of the onset of serious allergic reactions known as anaphylactic shock and remain elevated for more than a day afterwards. 

Using materials developed over a period of years in his research lab, Dr Walls has created a technique to measure these levels in patients and find out who is most at risk. This can radically change the way clinicians manage those affected.

Improving diagnosis

Dr Walls said: "The development of this test, should help to determine the proportion of people with a specific allergy who may be at risk of a life-threatening reaction.

"This advance allows clinicians to be able to understand the vulnerability of these patients, and either ensure they avoid the problem trigger, or provide them with an injection device so that they can self-administer a drug to fight the onset of a shock, vastly reducing their chances of continued serious attacks."

The novel idea is attracting interest from around the world and has been used extensively in clinical research studies with patients at Southampton General Hospital - as well as in complex cases from around the UK.

Dr Mich Lajeunesse, a consultant paediatric immunologist and a member of the clinical research team, said the test will drastically alter the way doctors diagnose.

"Severe allergic reactions are frequently overlooked by doctors who call it severe asthma instead," he said. "This test will help doctors recognise these reactions and provide patients with better aftercare and prevention of future allergic reactions."

He added: "If this test proves to be as useful as the early trials suggest, it is likely to become the gold standard for diagnosis of severe allergic reactions around the world."

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Page comments

Available evidence is limited, but does suggest that levels of CPA3 do change with time. Further research to examine systematically this important issue is currently being planned.
Dr Andrew Walls (07/12/2012 15:17:31)
I'd be interested to know if people's CPA3 levels are constant over time, e.g. if they outgrow an allergy. If my daughter has had an anaphylactic reaction to milk years ago, does that mean she has high CPA3 levels, even if she has outgrown her milk allergy? So her 'mild' hazelnut allergy is likely to be life-threatening on accidental exposure?
Anonymous (05/12/2012 22:33:15)
Sounds great. Being able to predict and hopefully prevent must be better and more cost effective all round.
Marina Murphy (21/12/2011 18:35:20)

Testing blood