Measurement of serum biomarkers
Serum total and specific IgE antibodies for common aeroallergens (Dermatophagoides farinae , cat dander, dog dander, birch,Alternaria alternata , and Humulus japonicus ) were measured using the ImmunoCAP system (Phadia, Uppsala, Sweden). Atopy was defined by positive specific IgE antibodies to at least one common inhaled allergen. Serum periostin was determined using the Human Periostin/OSF-2 DuoSet ELISA Kit (catalog number DY3548B; R&D Systems, Inc., Minneapolis, MN). Serum YKL-40 was determined using the Human Chitinase 3-like 1 Quantikine ELISA Kit (catalog number DC3L10; R&D Systems, Inc., Minneapolis, MN).