Relationship between serum IgE concentration and occurrence of immediate skin test reactions and allergic disorders in young people.

We studied serum IgE concentration by the PRIST method in 157 adolescents (71 boys) aged 15-17 years. This group was randomly drawn from a larger unselected population of 708 young people. The geometric mean IgE for the 157 subjects was 37.6 U/ml. After careful exclusion 77 subjects without any signs or symptoms of atopy were found. The mean IgE for them was 16.8 U/ml and the upper reference limit, calculated as mean +/- 2 SD of the logarithmic value, was 160 U/ml. Nineteen per cent of the population had an IgE concentration higher than 160 U/ml and 30% had a value below 20 U/ml. Positive skin test reactions were strongly associated with increased IgE values. Atopic eczema and allergic rhinitis also raised the IgE level, but the effect of bronchial wheezing was insignificant. We conclude that IgE concentrations above 160 U/ml during adolescence suggest atopy and correlate with positive skin test reactivity and/or clinical symptoms. An IgE value below 20 U/ml almost certainly excludes the possibility of positive skin reactions and somewhat less certainly the possibility that symptoms are due to atopy.