New Peanut Allergy Test Created That Cuts Out 'Risky' Food Challenge

Scientists have developed a new blood test to diagnose peanut allergies they believe is safer and more accurate than methods doctors currently use on patients.

If rolled out, the new test could catch a peanut allergy before patients have to undergo the oral food challenge (OFC)—widely regarded as the gold standard for identifying the condition. The OFC involves gradually feeding a patient incrementally larger amounts of peanuts, and must be carried out in a controlled hospital setting because of the risk of potentially life-threatening anaphylactic shock.

The new test boasts a 98 percent accuracy rate, and cuts the risk of false-positives. This occurs when the test suggests a person is allergic, even though they can eat nuts without suffering symptoms.

A peanut allergy is triggered when allergens react with an antibody called immunoglobulin E (IgE). This sets off symptoms ranging from itching skin to the throat and airways closing up. Digestive problems, such as stomach cramps and vomiting, are also common. The condition is most often diagnosed in young children, although it can develop later in life. Up to 15 million Americans have food allergies, including 5.9 million children under the age of 18.

Peanuts on sale at Eastern Market on Capitol Hill in Washington, DC, on June 27, 2008. Scientists say they have developed a more effective test for identifying peanut allergies. SAUL LOEB/AFP/Getty Images

The weapons in a doctor's arsenal to diagnose the condition also include a skin-prick test named after IgE, which measures the level of antibodies in a patient's system. But as this method can fail to spot the difference between a sensitivity and potentially dangerous food allergy, the test can lead to false-positives and over-diagnosis. If an IgE test is inconclusive, doctors can then carry out the oral food challenge (OFC).

Researchers believe the new method, which they have named the Mast Activation Test (MAT), could be used after the IgE test fails and before patients are referred for an OFC. The new test hones in on mast cells, a type of white blood cell activated when IgE is in the blood plasma. This produces biomarkers linked to allergic reactions, which can be identified in a lab. The process is also cheaper for clinicians, as the OFC must be done in the presence of hospital staff.

The researchers arrived at their findings by using blood samples from 174 children who were taking part in allergy testing. The study involved researchers from the U.K.-based Medical Research Council, Asthma UK Centre in Allergic Mechanisms of Asthma, and was published in Journal of Allergy and Clinical Immunology.

Dr. Alexandra Santos, a clinician scientist at King's College London, pediatric allergist and study lead author, told Newsweek that the MAT test is very specific, and means doctors can be sure if a patient has a peanut allergy.

"This is something we cannot conclude with current tests, such as skin prick test and specific IgE, which are often positive in children that are not allergic," she said.

"In many cases, in order to reach an accurate diagnosis, we have to perform oral food challenges in hospitals, which are resource-intensive and can cause patients to experience allergic reactions nd thus create stress and are risky. The MAT is more accurate than current allergy tests and could enable us to reduce the number of patients needing challenges."

The test could be rolled out in the U.K. in a few years, she said, although the procedure for introducing new diagnostics differs in the U.S.

MAT also has the potential to help patients already diagnosed with food allergies, as it could reveal whether the body's immune response has become less sensitive. The team is also working on tests for other food allergies such as milk and eggs.

Dr. Scott H. Sicherer, professor of pediatrics and director of the Jaffe Food Allergy Institute at Mount Sinai in New York and author of Food Allergies: A Complete Guide to Eating When Your Life Depends on It, told Newsweek that the new test is currently too labor-intensive, and further research is required before it can be added to current diagnostics.

"It looks like it may be a good research tool in the meantime," said Dr. Sicherer, who was not involved in the research.

Dr. Susan Leech, allergy expert and member of the U.K.-based Royal College of Paediatrics and Child Health (RCPCH), who was also not involved in the research, told Newsweek: "The gold standard for diagnosing peanut allergies remains the oral food challenge.

"There are a lot of advantages to the patient in performing the challenge–if there is no reaction, then the child can eat peanuts, but even if they do react, the food challenge provides information about what would happen if the child was to have a reaction, and gives an indication of what the threshold for the reaction would be.

"Further studies will need to be done to establish its use in determining whether or not a patient is outgrowing a peanut allergy–but at the moment, we have other tests for that."