PURPOSE OF THE STUDY.
To examine the accuracy of the ratio of serum immunoglobulin (sIgE) to total immunoglobulin E (tIgE; “Ratio”) in predicting the outcome of oral food challenges.
The study population was derived from an allergy outpatient clinic in Chicago, Illinois, from 2009 to 2013. The study included children aged 11 months to 18 years (median 4.0 years) with history of food allergy to milk, egg, soy, peanut, tree nuts, shellfish, or seeds, who underwent oral food challenges (OFC) to those foods and for whom food-specific (sIgE) and tIgE values were obtained.
This was a retrospective chart review. The Ratio was calculated by using the formula Ratio = (sIgE / tIgE) × 100. Multiple logistic regression models were used to assess statistical correlations between the outcome of OFC and the Ratio. Receiver operator characteristic curves were fitted, and the area under the curve was computed to compare the accuracy of the Ratio with sIgE alone in predicting the outcome of OFC.
One hundred sixty-one children underwent 195 challenges: 57% were boys, 76% were allergic to multiple foods, and 86% had atopic comorbidities. Overall, the Ratio for children who failed the OFC was higher than the Ratio for those who passed (failed 1.48% vs passed 0.49% n = 195). Area under receiver operator characteristic curves showed that the Ratio was more accurate in predicting OFC outcome (Ratio 0.69 vs sIgE alone 0.55; P = .03). However for less persistent food allergens (milk, egg, wheat, and soy), there was no significant difference in the median ratio for participants who failed their challenge than those who passed. In contrast, for challenges to more persistent food allergens (peanut, tree nut, seeds, and shellfish), the median Ratio for participants who failed their challenge was 2.18%, which was significantly higher than the 0.41% Ratio for those who passed their challenge (n = 93) (Ratio 0.81 vs sIgE alone 0.54; P < .01). The trend was independently observed for peanut and tree nut challenges though these were not statistically significant.
These finding suggest that using the Ratio may be more accurate that sIgE alone in predicting outcomes of OFC performed to confirm the development of tolerance to select food allergens, especially peanut and tree nuts.
The findings suggest that the Ratio may be a valuable added tool in the diagnosis of food allergy. Why would this be? Perhaps if there is more competition on the surface of the mast cell or basophil from “other” IgE antibodies, cross linking of sIgE for the food in question is less likely to activate the cells. However, the findings were only significant for more persistent food allergens. Why the study noted different influences of the Ratio for different foods remains to be determined but could represent a number of factors, including age of the children and atopic comorbidities at the time of OFC. The study offers an interesting insight, but the utility of a “fudge factor” in interpreting sIgE at different levels of tIgE needs additional study and validation.
- Copyright © 2015 by the American Academy of Pediatrics