Agreement of Total vs. Component Milk-Specific IgE ImmunoCAP Measurements DOI: https://doi.org/10.1016/j.jaci.2008.12.1067 Abstract RATIONALE: To determine the agreement between ImmunoCAP cow's milk-specific IgE measurements and IgE antibody responses to individual allergic milk protein components. METHODS: Sera from 30 children (6-16 years) with cow's milk allergy, 20 of which received milk oral immunotherapy (MOIT), were analyzed for IgE anti-cow's milk-(F2), alpha-lactalbumin-(ALA), beta-lactoglobulin-(BLG) and casein-(CAS) by Phadia ImmunoCAP. IgE anti-cow's milk levels alone were compared to the sum of individual IgE anti-alpha-lactalbumin;beta-lactoglobulin;casein in kUa/L. Bias/inaccuracy was assessed by deviation from an ideal ratio of 1.0. All IgE antibody levels >50 kUa/L were re-analyzed at dilutions to insure accuracy. RESULTS: Assuming the sum of IgE anti-ALA-BLG-CAS should accurately reflect, or possibly underestimate the total milk specific IgE, IgE anti-milk/summed IgE anti-ALA-BLG-CAS ratios for pre MOIT sera ranged from 2.17-1.74 (n = 2; over-estimate possibly due to missing IgE anti-BSA/lactoferrin), 1.04-0.90 (n = 3; equivalence) and 0.77-0.42 (n = 25, underestimate). In MOIT-treated subjects, IgE anti-milk/IgE anti-ALA-BLG-CAS ratios remained generally constant within each subject over a year of MOIT despite fluctuations in absolute IgE anti-milk levels and marked increases in IgG anti-milk. CONCLUSIONS: Patient-dependent bias can occur in which IgE anti-milk measurements alone may underestimate the actual level of IgE antibody reactive with milk components by up to 2.4 fold. While the concordance between the levels of milk-specific IgE antibody and the summed individual IgE anti-milk components is good for a minority of milk allergic patients, there is a majority where underestimation, possibly due to limited molar excess of components on the milk ImmunoCAP, may be substantial and clinically relevant. All Author: J. BogdanovicJ.M. Skripak A.W. Burks R.A. WoodR.G. Hamilton0