Determination of markedly elevated concentrations of specifi c IgE and index of specifi c IgE to Ambrosia artemisifolia allergen

Aim: to investigate the serum concentrations of total IgE (tIgE), specifi c IgE to birch allergen Bet v, and index of specifi c IgE (I-sIgE) in children with sensitivity to ragweed allergen Amb a, during ragweed pollen season. Methods: Children with asthma and/or rhinitis (N=121) sensitive to ragweed allergen Amb a. Concentrations of serum tIgE and sIgE to Amb a were determined by the use of standardized UniCAP-fl uoroimmunoassay method. Also, I-sIgE was calculated. Subjects were grouped in two subgroups: Subgroup 1a: (N = 70), children with sIgE to Amb a < 100 kIUA/L; Subgroup 1b (N = 51), children with sIgE to Amb a ≥ 100 kIUA/L. ROC-curve was used to defi ne cut-off value for I-sIgE for these subgroups. Results: Concentration of tIgE ranged between 41.5 to 5730 kIU/L, and concentration of sIgE between 2.5 - 991 kIUA/L. I-sIgE ranged between 0.01 - 0.53 [M (IQR) = 0.14 (0.08-0.26]. Values of I-sIgE were statistically higher (p < 0,0001) in Subgroup 1b - [M (IQR) = 0.28 (0.20-0.35], than in Subgroup 1a - [M (IQR) = 0.09 (0.07-0,13]. Cut-off value for I-sIgE-a between Subgroups 1b and 1a was >0.15 (sensitivity 87.3 %; specifi city 88%). Conclusions: I-sIgE to allergen Amb a may be used as useful additional biomarker of the degree of sensitization of patients.

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