Evaluation of the skin-prick test for predicting the outgrowth of cow's milk allergy

BACKGROUND Although considerable efforts have been made to develop diagnostic tools for predicting the outcome of oral food challenges, tests for predicting the outgrowth of food allergies are lacking. OBJECTIVE The aim of this study was to assess the diagnostic value of the wheal size and skin index (SI) (the ratio of an allergen-induced wheal to a histamine-induced wheal diameter) of the skin-prick test based on the outcome of a controlled oral provocation test for cow's milk. Moreover, we assessed whether wheal size and/or SI were useful for predicting the outgrowth of cow's milk allergy (CMA). METHODS This study included 135 children with suspected CMA. Eighty-one patients were definitely diagnosed by oral provocation tests for cow's milk, and their wheal diameters, SIs, and cow milk's-specific serum immunoglobulin E concentrations were determined. RESULTS The wheal diameters were significantly larger and the SIs significantly higher in children with positive oral provocation test results than in those with negative test results. We found that 50% of the patients were expected to be able to drink cow's milk by age 5 years. In these patients, the wheal diameters were significantly smaller and the SIs significantly lower at the time of CMA outgrowth than at the time of diagnosis, whereas these values were apt to increase in patients who did not outgrow CMA, with no significant difference. CONCLUSIONS The skin-prick test can be used to diagnose CMA and predict CMA outgrowth. A wheal diameter of 8 mm or/and an SI of 1.0 is informative, not only in diagnosing CMA but also in predicting a natural CMA outgrowth.