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

Background: Different laboratory assays are used to detect and measure spec ific IgE antibodies. No standard exists to assess their analytic performanc e. Objective: We sought to analyze reported specific IgE results from differen t 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 n ormal 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 ordina ry 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 laboratori es 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%). E xtensive variability was observed in the other 4 laboratory-assay systems w ith respect to overall average slope (0.76; range, 0.11-1.24), SE (0.19; ra nge, 0.03-0.95), R-2 value (53%; range, 0.00-0.98), and coefficient of vari ation (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 perfo rmed nearly as well as the ideal standard. Four of the laboratories-assays for specific IgE antibodies demonstrated substandard overall performance wi th multiple instances of poor precision and accuracy, particularly for cert ain allergens, such as weeds and molds.