Reducing the need for food allergen challenges in young children: a comparison of in vitro with in vivo tests

Background Double-blind placebo-controlled food challenges (DBPCFC), the go ld standard for the diagnosis of food hypersensitivity, are time-consuming and not without risk. We have recently reported skin prick test (SPT) weal diameters to cow's milk, ego and peanut above which infants and young child ren referred for investigation of suspected food allergy showed an adverse reaction on food challenge. We have termed these the '100% diagnostic SPT l evels'. In this study, we compare in vivo with in vitro measurement of IgE antibody levels to three common food allergens-cow's milk, egg and peanut i n infants and young children with suspected food allergy, in order to reduc e the need for food challenges. Methods SPT and Enzyme Allergo-sorbent Test (EAST) (from 1992 to 1998) and CAP values (from 1999 to 2000) were performed in 820 children < 2 years of age with suspected allergy to cow's milk and/or egg and/or peanut. SPT leve ls previously shown to be diagnostic of challenge-proven allergy to cow's m ilk, egg and peanut were used as the '100% diagnostic SPT levels' and compa red with EAST and CAP values associated with IgE food allergy according to the manufacturer's definition. Results McNemar's test showed a significant difference between the '100% di agnostic SPT levels' and positive EAST in identifying patients who did not require food challenge for cow's milk (P=0.01), egg (P<10(-6)) and peanut ( P<10(-6)), and a significant difference between the '100% diagnostic SPT le vels' and positive CAP (P <10(-6)) for egg and peanut but not cow's milk. T wenty-three per cent of food challenges which, based on the results of EAST and CAP, would have been necessary to confirm the diagnosis of food allerg y were avoided by the use of the '100% diagnostic SPT levels'. Conclusion The use of the '100% diagnostic SPT levels' compared with in vit ro measurement of IgE antibody to cow's milk, egg and peanut reduces the ne ed for food challenge in young children with suspected food allergy.