Analytic precision and accuracy of commercial immunoassays for specific IgE: Establishing a standard

Background: Different laboratory assays are used to detect and measure specific IgE antibodies. No standard exists to assess their analytic performance. Objective: We sought to analyze reported specific IgE results from different laboratories on the same serum samples for their accuracy and precision. Methods: Blinded serum samples (26) containing variable levels of specific IgE to 17 common aeroallergens were sent on 3 different occasions through normal channels to 6 laboratories that used 5 different test procedures. Six samples were presented as a dilution series. Laboratory-assay performance was assessed by analyzing the reported results (n = 12,708) by using ordinary least squares regression with slope coefficients, the t statistic, SEs, confidence intervals, and R 2 values. These were compared with a theoretic ideal assay as the reference. Results: Analysis revealed that one system used in two different laboratories performed nearly as well as the ideal standard, with an overall average slope (0.97; range, 0.91-1.01), SE (0.05; range, 0.02-0.16), R 2 value (93%; range, 0.64-0.99), and coefficient of variation (10.3%; range, 6%-14%). Extensive variability was observed in the other 4 laboratory-assay systems with respect to overall average slope (0.76; range, 0.11-1.24), SE (0.19; range, 0.03-0.95), R 2 value (53%; range, 0.00-0.98), and coefficient of variation (19%; range, 5%-49%). For some specific allergens, some laboratories-assays were not able to detect serial dilutions of the same sample. Conclusions: One commercial system used in two different laboratories performed nearly as well as the ideal standard. Four of the laboratories-assays for specific IgE antibodies demonstrated substandard overall performance with multiple instances of poor precision and accuracy, particularly for certain allergens, such as weeds and molds. (J Allergy Clin Immunol 2000;105:1221-30.)