Phadia immunocap system

Total immunoglobulin E (IgE), as well as IgE specific for food allergens (fx5) or inhalative allergens (sx1) were determined at children’s age of 10 years by Phadia ImmunoCAP system (Thermo Fisher Scientific, Freiburg, Germany) from serum samples. Total IgE concentration >34.6 kU/l was classified as “increased,” as well as specific IgE (sx1 or fx5) >0.35 U/l (29 (link)). Values below the detection limit were included in the analyses using half of the defined detection limit.

In all 3 surveys blood samples were obtained and processed under similar conditions. After clotting and centrifuging, serum was stored at −20°C until analysis in a single central laboratory (Pharmacia Uppsala in 1992, Kings College London in 2002, and AMC Amsterdam in 2013/2014) by using the Phadia ImmunoCAP system (now Thermo Fisher Scientific, Uppsala, Sweden).
To assess the effects of potential laboratory bias on the prevalence of IgE sensitization and the mean of total IgE estimates, we conducted duplicate assays on 794 samples (tested at ECRHS I, stored, and tested at ECRHS II) and 475 samples (tested at ECRHS II, stored, and tested at ECRHS III; see Table E1 in this article's Online Repository at www.jacionline.org). The methods for this correction are described in detail in the Methods section in this article's Online Repository at www.jacionline.org.

Twenty allergic patients were recruited from the allergy clinic of the Division of Allergy, Immunology, and Rheumatology of Taichung Veterans General Hospital. All allergic patients were sensitive to storage mite-T. putrescentiae and had mite-specific IgE as determined by the Phadia ImmunoCAP system (Thermo Fisher Scientific Inc. Waltham, MA., USA). The diagnosis criteria of asthma were used according to guidelines of the Global Initiative for Asthma (GINA) guideline 2018. Diagnosis of allergic rhinitis was based on Allergic Rhinitis and its Impact on Asthma (ARIA) guideline 2016. All patients were advised to stop the anti-allergy medication for at least 2 weeks prior to attending this study (those who could not stop anti-allergic drugs or with acute allergic symptoms were excluded). Ten non-allergic healthy volunteers were recruited as control. The study was approved by the Research Ethics Committee of Taichung Veterans General Hospital (TCVGH IRB No. C07126). All individuals for this study provided written informed consent. The peripheral venous blood sample was collected from recruited volunteers and was immediately processed to fractionate plasma and cells for further analysis.