Total serum IgE as a parameter to differentiate between intrinsic and extrinsic atopic dermatitis in children.

Atopic dermatitis (AD) has been sub-classified into extrinsic and intrinsic types according to the presence or not of allergen-specific IgE antibodies. Although total serum IgE levels are frequently elevated in AD, their potential to predict allergen-specific IgE (asIgE) has rare ly been studied. We investigated 103 children with AD and suspected allergen-specific sensitization. A thorough clinical examination, a structured medical history and total serum IgE and asIgE measurements were performed. Fifty-three male and 50 female patients, median age 35 months (range 3 months to 17 years), were recruited. Sixty-three percent of patients were asIgE positive, while 37% did not reveal such IgE antibodies; median total serum IgE levels were 224.0 kU/l (14-12,013 kU/l) and 25.2 kU/l (0-4352 kU/l), respectively. Associations of asIgE status with atopic co-morbidity and total serum IgE levels were statistically significant. At a cut-off total serum IgE level of 106 kU/l (sensitivity 68.7%; specificity 92.3%), positive and negative predicted values (93.6% and 64.3%, respectively) were determined. Clinical decision points predictive of positive asIgE results were identified in 90%, 95% and 99% of patients, respectively. Total serum IgE values were significantly associated with the asIgE status of investigated patients. However, these preliminary data warrant further large-scale investigations before total serum IgE levels can be regarded as a clinically useful parameter between patients with extrinsic atopic dermatitis and intrinsic atopic dermatitis.