A new blood test could make diagnosing peanut allergies a safer and cheaper process.
Scientists from the Medical Research Council in the United Kingdom have developed a test that they say doesn’t run the risk of false positives or cause patients to go into anaphylactic shock.
The current method for diagnosing a peanut allergy uses a skin prick or IgE test to check for specific antibodies. But these exams can result in overdiagnosis and false positives.
When such tests are unclear, doctors undertake an oral food challenge. In this, patients are fed peanuts in increasing amounts in a controlled hospital setting.
While the test is the most reliable for diagnosing food allergies, there’s risk of causing severe allergic reactions.
The scientists from the Medical Research Council say their new test carries less risk and is also five times more cost effective than the oral food challenge.
“Food challenges are the gold standard to diagnose food allergies… but they carry the risk of causing allergic reactions, including anaphylaxis. They take a long time, one day in hospital. They require equipment and staff experienced in treating allergic reactions and thus are very costly, and currently there are long waiting times for this procedure in the centers that can offer it to patients,” Dr. Alexandra Santos, a pediatric allergist at King’s College London and lead author of the study, told Healthline.
The new blood test, called the mast activation test (MAT), could act as a secondary tool if skin prick test results are inconclusive.
“The mast cell activation test can complement existing tests, like skin prick test and IgE test in the blood, which are often positive in individuals that are not allergic. The MAT is highly specific, meaning that when it’s positive it confirms peanut allergy with high certainty, reducing the number of patients needing challenges and particularly the number of patients reacting during challenges,” Santos said.
The new test looks at mast cells, which play an important part in triggering an allergic reaction.
In developing the test, the researchers used blood samples from 174 children undergoing allergy testing. Of them, 73 were allergic to peanuts and 101 were not allergic.
The researchers added peanut protein to mast cells and then screened for activated mast cells.
They said the MAT identified peanut allergies with a 98 percent specificity. The test also showed the severity of the peanut allergy. The more mast cells that were activated, the more severe the reaction.
A promising alternative
Allergy experts say the new test sounds promising.
“This could be a game changer if the data supports the test accuracy and reliability in appropriate diagnosis,” Tonya Winders, chief executive officer of the Allergy and Asthma Network, told Healthline.
“At this point, the [oral food challenge] is the only definitive test to determine if a person is truly allergic. This new test holds promise of a less invasive, less risky option to make this diagnosis,” she added.
Santos says the current tests for the allergy aren’t ideal and can produce misleading results.
“If we relied on them alone, we’d be overdiagnosing food allergies. Only 22 percent of school-aged children in the U.K. with a positive test to peanuts are actually allergic when they’re fed the food in a monitored setting,” she said.
Dr. Richard Lockey, director of the division of Allergy and Immunology at the University of South Florida College of Medicine, says overdiagnosis of food allergies is a common problem.
“The average physician knows little about allergy, particularly food allergy, so when they see a positive test they tell the patient not to eat the food, even though they’ve been eating the food all along without any problems,” he told Healthline. “Food tests shouldn’t be done unless there’s a positive history of a reaction to a food, in this case peanuts.”
What the future holds
It may still be a few years before this test is routinely used.
Researchers are also adapting the test for other uses.
“We are now developing this test for other food allergies, such as milk, egg, other nuts and seeds. Apart from its diagnostic applications, the MAT could be used to monitor improvement in patients undergoing treatment for food allergy and to detect the presence of food allergens in foodstuff,” Santos said.
Should the test be made available for widespread use, the number of people needing to undertake an oral food challenge would decrease, as would the risk of associated allergic reactions.
Santos says this would make testing for allergies much more pleasant for patients, as well as more accurate.
“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,” Santos said.