Serum IgE concentration was measured on the 5th day of life in 943 infants. All infants were included in a 3 month follow-up study. The frequency of cow's milk allergy was studied according to either family history, IgE level, or both. Feeding (mother's milk or formula feeding) was taken into account.
Manifestations suggestive of food allergy were hardly observed in breast-fed babies. In the formula-fed group a positive family history correlated with a 40% incidence of allergic manifestations, compared to a 13% incidence (P<0.001) in the group with negative family history. A high IgE level (IgE>1.3 U/ml) indicated a 43% risk of developing allergic manifestations in formula-fed babies as compared to 15% (P<0.001) in the group with normal results of a screening test.
Frequency of allergic manifestations in a subgroup with a negative family history and a high IgE level (38%) was equal to the frequency in the subgroup with a positive family history and negative screening test results (IgE<1.3 U/ml) (36%). The incidence in the subgroup with both positive screening test results and a positive family history was 49%. None of these differences were significant. The frequency in the subgroup with both parameters negative was 8% (P<0.001 to 3 other subgroups).
Our results indicate that the family history seems to correlate as well with the incidence of allergic manifestations as the neonatal serum IgE concentration. Serum IgE concentration as a neonatal screening test for allergy provides significant information about the risk of developing allergy compared to the family history only in formula-fed babies with a negative family history. This could be an important factor in improving the cost/benefit ratio of screening programs for allergy.