Simple and accurate test for peanut allergy

By Dr. Ananya Mandal, MDMar 21 2012

Australian researchers have developed a new method of testing children for peanut allergies providing for a less invasive and more accurate diagnosis.

The Murdoch Children’s Research Institute and University of Melbourne researchers discovered a two-pronged blood test will confirm peanut allergies instead of putting children through risky oral food challenge tests.

Associate Professor Katie Allen said the blood testing process reduced the need for oral food challenges “four-fold”, which also cuts the unnecessary risks of reactions, like anaphylaxis. “(The existing test) can be dangerous and expensive,” Ms Allen said. “The waiting list for the oral food challenge in Melbourne alone is one to two years long so this test is going to free up already overwhelmed health services.”

Peanut is the most common nut allergy - affecting about 3 per cent of Australian children under the age of two. She said researchers had spoken to many parents who said they feared giving their children peanuts but wanted to know if they were allergic, so they fed their children peanuts in the car parks of hospitals so they could head straight in if they had an adverse reaction. “There is so much concern about it,” Ms Allen said.

The new testing process includes taking blood to screen for a peanut allergy. Using the same blood sample, the next stage tests for a peanut protein called “Arah2”, which is the most common peanut allergen detected in children and the most common allergen overall in Australia. If the blood is found to have Arah2 in it, a peanut allergy is confirmed and no further testing is needed.

The institute's researchers carried out the tests on a group of 5300 infants from across metropolitan Melbourne. About 200 of those who had peanut allergies confirmed through oral tests were accurately diagnosed by the two-stage screening process.

Ms Allen said the study found this method would reduce over-diagnosis of peanut allergies and cut the number of people referred to specialists for further testing. “We have people who have had a positive skin prick test who have never eaten a peanut and for 15 years may have been inadvertently avoiding a food they weren't even allergic to,” she said. “At the other end of the spectrum we have people where we ... have to put them through potentially dangerous tests where there is an anaphylaxis risk.”

The test is ideal for those children who are at high risk of food allergies, like those with eczema, but also for those who have never been exposed to peanuts before.

Dr Allen said it was hoped support could be provided to train pediatricians and GPs to use the test, reducing specialist waiting list times, which vary from 18 months and up to two years for oral tests. “It's very hard for people to get into see us because we are so overwhelmed, so this is a desperate attempt to try to improve patient accessibility so we can provide the most appropriate care for the patients in the community that need it.”

The study was recently published in the Journal Of Allergy And Clinical Immunology.