Blood collection
Serum sIgE and IgG4 to peanut and peanut components (rAra h 1, rAra h 2, rAra h 3, rAra h 8) were determined by ImmunoCAP (Thermofisher, Uppsala, Sweden). Peanut component sIgE was assayed for participants with a peanut IgE ≥0.1 kUA/L; for subjects with levels <0.1KU/L, an imputation was performed. A ratio of Ara h 1, h2 and h3 to peanut sIgE was calculated to examine the distribution of each component in relation to sIgE to peanut. The median of this ratio was used to determine the imputed value for each Ara h component for patients who had peanut sIgE<0.1kUA/L. The ratio of peanut-specific IgG4:IgE was calculated after peanut-specific IgG4 levels were converted from µg/L to ng/mL and peanut sIgE levels were converted from kU/L to ng/mL using the formula (IgG4 ÷(IgE x 2.4)). (12) Plasma or serum was also used for MAT.