Scientists at the Medical Research Council (MRC), UK, have developed a simple blood test which will be a less risky and more definitive way to diagnose a peanut allergy.
The peanut allergy blood test has reportedly a 98% specificity and doesn’t have the risk of false positives or causing allergic reactions such as anaphylactic shock like the current options do.
By using this new blood test, it becomes five times more cost-efficient compared to the oral food challenge (OFC), the standard food allergy test, as well being adaptable to test for other food allergies.
The current methods
Doctors currently diagnose a peanut allergy by using a skin-prick or specific immunoglobulin E (IgE) test; however, this can result in over-diagnosis or false positives, and it can’t differentiate between sensitivity and true food allergy.
If these tests are definitive, allergists try an OFC, which involves feeding increasingly larger doses of peanut to a patient in a controlled environment to get the allergy confirmed.
Despite its accuracy, there is a serious risk of severe allergic reactions.
What is the new test?
The new test aims to improve on this. Called the mast activation test (MAT), it could act as a second-line tool when skin-prick test results are not definitive, therefore avoiding referral to specialists for an OFC.
Dr Alexandra Santos, MRC clinician scientist at King’s College London, UK, 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.
“The new test is specific in confirming the diagnosis, so when it’s positive, we can be very sure it means allergy. We would reduce by two thirds the number of expensive, stressful oral food challenges conducted, as well as saving children from experiencing allergic reactions.”
How it works
Instead of measuring the presence of IgE antibodies, which food allergens activate and then trigger symptoms such as skin reactions and digestive problems, it focuses on mast cells, which play a crucial role in triggering allergic reactions.
According to a release from the MRC, mast cells activate by recognising the IgE in plasma and, in allergic patients, produce biomarkers associated with allergic reactions, which can be detected in the lab. The MAT is five times cheaper than the OFC.
Santos added: “We are adapting this test to other foods, such as milk, eggs, sesame, and tree nuts. This test will be useful as we are seeing more and more children who have never been exposed to these foods because they have severe eczema or have siblings with allergies.”
The Food Standards Agency estimates that 5-8% of UK children have a food allergy.
Source: Medical Research Council