Predicting skin test sensitivity and total serum IgE levels in family members.

A total of 278 individuals in 42 randomly ascertained nuclear families were studied to determine correlations among family members for skin test response and total serum IgE levels. The major aim was to determine whether these measures of allergic response in family members could be used to predict whether the last child in the family would be skin test positive. There were significant correlations in total log[IgE] levels between parents and their children and an even higher correlation between siblings. For the measurement of skin test response (allergy index), the only significant correlation was between siblings. Discriminant analysis was performed with the fourth child in the family as the index case. This was done to determine how many of the index cases could be correctly predicted to be skin test positive or negative based on family information. With just the skin test results on the parents, only three of the 13 positive index cases were correctly predicted. However, when the mean value for the skin test results in the siblings (mean allergy index) was used, eight of the 13 skin test positive index cases were correctly predicted. These results suggest that, although there is a high degree of concordance for allergic disease within families, information from other siblings may be the most useful predictor of allergic status in another child.