A new blood test trumps traditional diagnostic methods for determining peanut allergy, the most common allergy for children. From the Medical Research Council, scientists introduce a new, extremely accurate and dependable test for detecting peanut allergies and potentially other common food allergies.
Existing tests to diagnose peanut and other food allergies include the immunoglobulin E (IgE) test, skin prick test, and oral food challenge (OFC). The IgE test measures the amount of an antibody produced by the immune system in response to allergens, which are recognized as if they were dangerous invaders. The skin prick test involves exposing the skin to potential allergens, looking for signs of inflammation that could signal an allergy. Lastly, the golden standard for diagnosing food allergies is the OFC, where individuals consumes increasing increments of a potential allergen in a controlled setting. Despite the safety measures, the OFC still runs the risk of causing dangerous allergic reactions.
"The current tests are not ideal. If we relied on them alone, we'd be over diagnosing food allergies - only 22 per cent 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,” explained lead author Alexandra Santos.
The new mast activation test (MAT) scans the blood for mast cells, immune cells involved in initiating allergic reactions. Mast cells respond to IgE in plasma and produce biomarkers associated with allergic reactions.
The MAT test greatly reduces the risk of false-positive results or dangerous allergic reactions like anaphylactic shock. It has shown to be five times more cost-efficient than the OFC, and it could be adapted to test for other food allergies. Additionally, the test’s close precision allows it to help doctors distinguish sensitivity to an allergen from a true food allergy.
"The new test is specific in confirming the diagnosis so when it's positive, we can be very sure it means allergy,” Santos 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."
Santos’s study involved 174 blood samples from 73 children with peanut allergies and 101 without them. Via the samples, researchers added peanut protein to mast cells to evaluate any IgE-mediated activation, indicating an allergy. The test successfully detected peanut allergy with 98 percent specificity. Even more, the test indicated the severity of the allergy, a quality that’s associated with higher mast cell levels.
"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,” Santos said. “Parents are often afraid to feed them a food that is known to cause allergic reactions."
The present study was published in the Journal of Allergy & Clinical Immunology.