An experimental blood test may help to diagnose the severity of food allergies, according to a recent study published by a team of Mount Sinai Hospital researchers in the Annals of Allergy, Asthma & Immunology. Results of the study showed that the blood test, called the basophil activation test or BAT, correlated well with oral food challenges, which are considered to be the "gold standard" tests for food allergies.
In the U.S., food allergies affect approximately 4%–6% of children and about 4% of adults, according to the Centers for Disease Control and Prevention, and are a growing public health concern. About one-third of affected children have a history of severe reactions. Foods that cause 90% of serious reactions include eggs, fish, milk, peanuts, shellfish, soy, tree nuts and wheat.
Food allergies occur when a person's immune system has a specific response to certain foods. The reaction can sometimes be overwhelming, with signs and symptoms such as itching or swelling in the mouth, hives, diarrhea, cramps and/or vomiting, trouble breathing and tightening of the throat. A reaction may even lead to anaphylaxis, a potentially life-threatening condition.
Currently, health practitioners usually administer oral food challenges to diagnose food allergies. These involve giving a person small amounts of foods that might cause reactions (allergens) and monitoring for allergic reactions. This can be time-consuming and labor-intensive, and the person tested must be watched carefully for any severe reactions. Furthermore, oral food challenges and other current allergy tests, such as blood tests for allergen-specific IgE antibodies and skin prick tests, are not able to predict how severe a person's reaction to an allergen might be.
In this study, the Mount Sinai researchers investigated the basophil activation test as a potential new way to help diagnose food allergies and perhaps predict severity of the reactions. The test requires collecting a sample of blood from a vein in the arm. Basophils are one type of white blood cell. The test counts the number of basophils in the blood sample that are activated when exposed to extracts of different foods (allergens).
The researchers collected blood samples from 67 patients, who ranged in age from 12 to 45 years old, and tested the samples using the basophil activation test. The patients then underwent food challenges and were given an item that contained no allergen (placebo) or a food allergen such as peanut, fish, etc. The study was a randomized double-blind study, which means the items were given randomly and the researchers and patients did not know who received placebos or allergens.
Results of the study showed a good correlation between basophil activation test results and the severity of reactions from the food challenges. Though the study was small, the results provide some evidence that the basophil activation test may be helpful in predicting severity of food allergies. The test was better at predicting the severity of the allergic response than other currently used tests.
"This blood test could improve the diagnosis of allergy to foods, and reduce the need for oral food challenges," said Dr. Xiu-Min Li of the Icahn School of Medicine at Mount Sinai, New York.
"Having blood drawn for BAT is a much less difficult procedure than food challenges," said Dr. Ying Song, also a researcher at Mount Sinai Hospital. "Although food challenges are widely practiced, they carry the risk of severe allergic reactions, and we hope that BAT can be developed further to provide accurate information in a safe manner."
The basophil activation test is not currently available in clinical settings. However, if results from additional research with larger studies continue to be promising, it may become a useful test at some point in the future.