New peanut allergy blood test developed

Scientists have developed a blood test for peanut allergies that they say is less risky and more cost-efficient than other tests.

The skin-prick test used currently can result in people being diagnosed with an allergy when they do not have one.

And the new test could be used after inconclusive skin-prick tests instead of tests that involve eating nuts.

The Medical Research Council team says new the test could be adapted to test for other food allergies.

The current oral food challenge (OFC) involves feeding peanuts in increasingly large doses to a patient in a controlled setting in hospital to try to confirm the allergy.

However, it has a risk of causing severe allergic reactions. And the researchers say the new test is safer and more accurate.

Their study, published in the Journal of Allergy and Clinical Immunology, involved 174 children aged from six months to 17 years, 73 of whom were allergic to peanuts.

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The study's lead author, Dr Alexandra Santos, of King's College London, said: "The current tests are not ideal.

"If we relied on them alone, we'd be over-diagnosing food allergies - only 22% of school-aged children in the UK with a positive test to peanuts are actually allergic when they're fed the food in a monitored setting."

Food allergy symptoms

The symptoms of a food allergy usually start within seconds or minutes of eating the food.

They include:

• tingling or itching in the mouth

• a raised, itchy red rash

• swelling of the face, mouth, throat or other parts of the body

• difficulty swallowing

• wheezing or shortness of breath

• feeling dizzy or light-headed

• feeling sick or vomiting

• abdominal pain or diarrhoea

• hay-fever-like symptoms

Source: NHS Choices

Dr Santos told the BBC oral food challenges, conducted in hospital with an allergist and two nurses with an individual patient, who needs constant monitoring, "require access to sophisticated medical facilities needed to treat severe allergic reactions should they develop, which can be very expensive".

"The new test is specific in confirming the diagnosis. So when it's positive, we can be very sure it means allergy," she said.

"We would reduce by two-thirds the number of expensive, stressful oral food challenges conducted, as well as saving children from experiencing allergic reactions.

"One of the advantages for its use on the NHS is the fact that it is less expensive and safer compared to the OFC, but proper cost-effectiveness studies and studies about the wider impact of the test need to be performed once it is indeed available to the clinicians.

"Before it can be used clinically, it needs to be running routinely in a diagnostic laboratory."

Holly Shaw, nurse adviser at Allergy UK, told the BBC: "We welcome food-allergy focused research, an area of concern for health professionals and those whose lives are impacted on by food allergy.

"Research in this area enables scientists and clinicians to further improve their understanding and make advancements in diagnostic testing."