Some allergists say diagnosing a food allergy can be as much an art as it is a science. That’s because current diagnostic tests don’t give doctors a clear picture of a patient’s allergies. False-positive results make available diagnostic tools challenging for doctors and burdensome for patients. Food allergy diagnostics rarely offer patients details about their allergy and can never predict future symptoms or severity of possible reactions. Patients and allergists need simple diagnostic tools that deliver definitive results, offer better guidance to patients, and are accessible to all.
There are three diagnostic tests in use today: the skin prick test, IgE blood tests, and an oral food challenge.
Skin Prick Test (SPT):
As its name suggests, the skin prick test relies on a skin reaction. In a medical office, a small amount of allergen is placed on a patient’s skin (typically on the arm or back) with a plastic toothpick that scratches the surface of the skin. Within 15-30 minutes, the doctor measures any large bumps that may emerge – these are known as wheals and their size suggest sensitivity to each allergen. This test can be uncomfortable and not well tolerated by people who have severe eczema or who need to remain on antihistamines. SPTs have a high rate of false-positive results. False-negative results are also not uncommon in young patients.
IgE Blood Tests (including component tests):
Blood tests that measure the immunoglobin E (IgE) antibody are another method of diagnosing a food allergy. IgE is the antibody that causes your immune system to react abnormally to certain food resulting in a food allergy. Also known as RAST (for radioallergosorbent test) or ImmunoCAP test, a patient’s blood sample is tested against suspected allergens in a lab. It typically takes several weeks to process this test and false positive results are common. Each version of IgE test relies on its own scale of results, so it is critical that a healthcare provider be familiar with how to interpret and compare the results properly.
Oral Food Challenge (OFC):
The oral food challenge is the only definitive test for food allergies and is considered the gold standard of allergy diagnosis at present. This test takes place under medical supervision and is long in duration (often 4-5 hours). True to its name, patients are given increasing amounts of their allergen to assess overall tolerance. This test is generally the most stressful for patients as they are wary of consuming a food they have been told to avoid. Taste and texture aversions can make eating these foods difficult in patients of all ages, most especially young children. Caregivers are often concerned about subjecting their children to oral food challenges unless it would result in a major improvement in diet or safety. Finally, an OFC has many lifestyle restrictions for patients during the weeks before and immediately after their challenge. Patients must go off of any oral antihistamines 1-2 weeks before their challenge which can make it difficult to schedule during certain seasons. Challenges must be postponed if the patient has a cold or virus, fever, or needs emergency asthma medications. And among other restrictions, patients cannot engage in rigorous physical exercise in the hours before or after the test.
The Problem with False Positives
Although each diagnostic tool has their advantages and disadvantages, SPTs and blood tests are known for their high rate of false positives. In fact, skin prick tests have a false positive rate of 50 percent. False positive rates for blood tests are even higher, making it possible for patients to be misdiagnosed with a food allergy they don’t actually have. This is known as overdiagnosis.
The negative impacts of overdiagnosis is threefold. First, false positive results mean a patient may be told to strictly avoid food unnecessarily. This can place tremendous stress and undue burden on the patient and their family. Food avoidance – which is the standard treatment for food allergy – is complicated and often challenging to manage. Living in total avoidance of an allergen is physically and emotionally demanding, nutritionally depleting, and expensive. Free-From food – that is food that is made to be allergy-friendly – can cost up to five times more than the cost of its regular counterpart. Reading food labels can be time-consuming. Cross contact outside the home and in manufacturing can make finding safe food a challenge. Food avoidance also impacts social interaction as patients and caregivers are forced to protect themselves in school, at work, and amongst family and friends.
Second, a misdiagnosed patient may become truly allergic by missing the window for early introduction and regular consumption of allergenic food. According to the LEAP study (Learning Early About Peanut Allergy), researchers found that introducing peanuts to an infant’s diet early (between 4-11 months) reduced their risk of developing a peanut allergy by 70-80 percent.1 Misdiagnosis followed by allergen avoidance may hasten the development of a food allergy in susceptible patients.
Lastly, patients are forced to undergo multiple diagnostic tests so that their healthcare provider can get a better sense of their allergy from multiple perspectives. This is draining and expensive for all patients but is particularly taxing for children who are more nervous and uncomfortable during these procedures.
The Future of Food Allergy Diagnosis
For the safety and sanity of patients, food allergy diagnostics need to be able to correctly direct new patients into the food allergy treatment pipeline and safely release those who do not need to be there. Without a cumbersome oral food challenge, today’s diagnostic tests don’t do this.
But there is cause for hope. A new product by Allergenis is set to be released in 2022 that can fill the gap left by current food allergy tests. Allergenis’ Peanut Diagnostic can determine an allergy with 93% accuracy, far outperforming the SPT and IgE blood tests. But that’s not all. As a result of years of research with the best minds in food allergy, Allergenis’ product can predict a patient’s threshold – previously only available by undergoing an oral food challenge. While we all understand that threshold – that is, the amount of protein that would trigger a reaction – is influenced by co-factors (such as illness, hormone changes, and exercise), this new information allows patients to track overall changes in their allergy, evaluate possible treatment options, potentially shorten treatment time, and discuss if and how a patient’s threshold affects their lifestyle with their allergist. With Allergenis’ Peanut Diagnostic, peanut allergy is no longer binary.
Allergenis’ Peanut Diagnostic offers patients and healthcare providers much-needed details about food allergies in a single blood test. Physicians will be able to guide patients toward a safer, fuller, more enriching life. And patients will be able to take their food allergies into the world with more confidence than ever before.
You can learn more at enjoylifeintheknow.com and sign up to be notified when testing is available.
- Du Toit G., Roberts G., Sayre R., Bahnson H., Radulovic S., Santos A., Brough H., Phippard D., Basting M., Feeney M., Turcanu V., Sever M., et al. Randomized Trial of Peanut Consumption in Infants at Risk for Peanut Allergy. N. Engl J Med. 2015; 372:803-813.