Currently, the only reliable way to diagnose a food allergy is through an oral food challenge, which is not only expensive and time consuming, but may also result in the child having a severe allergic reaction, also known as anaphylaxis.
Graham Roberts, DM and colleagues from Imperial College at St. Mary's, London, United Kingdom, examined the ability of skin prick and specific IgE testing to accurately predict the presence of food allergy to peanuts, the most common childhood food allergen.
95 Percent Predictive
They examined 157 children with a history suggestive of peanut allergy. All of the children underwent skin prick testing to peanut, a blood test for peanut-specific IgE and an oral food challenge to prove or disprove their food allergy. The researchers demonstrated:
- Based on peanut skin prick test results, a wheal measurement of 8mm or greater had a positive predictive value of 95 percent for a positive oral challenge to peanut.
- Based on blood tests, a peanut specific IgE of 15 kUA/L or greater had a positive predictive value of 92 percent.
Avoiding the Oral Food Challenge
This study demonstrates that a skin prick test of at least 8mm or a specific IgE test of at least 15 kUA/L can accurately predict clinical peanut allergy in these children. Based on these findings, researchers developed likelihood ratios using the strength of a patient's history and the skin prick or specific IgE results to determine the probability that a food allergy exists.
Researchers believe the use of these results by family practitioners, pediatricians, and allergists should reduce the need for children with possible food allergy to undergo an oral food challenge. Further studies need to be undertaken to extend these findings to other highly allergenic foods.