Proficiency survey-based evaluation of clinical total and allergen-specific IgE assay performance

Context.-The diagnostic algorithm for human allergic disease involves confirmation of sensitization by detection of allergen-specific immunoglobulin E (IgE) antibody in individuals suspected of having allergic disease because of a history of allergic symptoms after known allergen exposure. Previous studies showed wide disparity among clinically reported allergen-specific IgE levels from different serologic assays. Objective.-To validate the relative analytic performance (sensitivity, interassay reproducibility, linearity/parallelism, intermethod agreement) of clinically used total and allergen-specific IgE assays by using College of American Pathologists' Diagnostic Allergy "SE" Proficiency Survey data. Design.-Data from 2 SE survey cycles were used to assess relative analytic performance of the ImmunoCAP (Phadia), Immulite (Siemens Healthcare-Diagnostics), and HYTEC 288 (HYCOR-Agilent Technologies) total and allergen-specific IgE assays. In each cycle, 2 recalcified plasma pools from atopic donors were diluted twice with IgE-negative serum and evaluated in approximately 200 federally certified clinical laboratories for total IgE and IgE antibody to 5 allergen specificities. Statistical analysis evaluated analytic sensitivity, linearity, reproducibility, and intermethod agreement. Results.-Interlaboratory intramethod, intermethod, and interdilution agreement of all 6 clinically used total serum IgE assays were excellent, with coefficients of variation (CVs) below 15%. Interlaboratory intramethod, and interdilution agreement of 3 clinically used allergenspecific IgE assays were also excellent with CVs below 15%. However, intermethod CVs identified between-assay disagreement greater than 20% in 80% of allergen-specific IgE measurements. Allergen reagents and patients' immune response heterogeneity are suggested probable causes. Conclusions.-Clinical total and allergen-specific IgE assays display excellent analytic sensitivity, precision, reproducibility, and linearity. Marked variability in quantitative estimates of allergen-specific IgE from clinically used automated immunoassays is a concern that may be ameliorated with component allergen use.