Precision and inter-laboratory correlation of specific IgE determinations by modified RAST

Standardization of test results depends on the reproducibility of a given m ethod among laboratories. The purpose of this study was to demonstrate that modified radioallergosorbent test (mRAST) continues to be a very reliable test for the diagnosis and monitoring of allergic patients. The reproducibi lity of allergen-specific IgE results obtained with the mRAST was investiga ted in five laboratories. Blinded replicates of patient serum samples were sent to each laboratory for specific IgE determinations by mRAST using eith er a 2-day or 3-day protocol. The same reagents were used at all laboratori es, including the same lot numbers of allergens. Inter-assay precision for inhalant allergens within laboratories was 4.0 to 16.0 percent CV, comparab le to other commercially available assays. The allergy class scores from al l laboratories were in very good agreement, with 97.1% to 99.2% within one class of the reference laboratory. Linear regression of radioactive counts data indicated that repetitive runs within and between laboratories were ve ry reproducible, with slopes bracketing the ideal value of 1. Comparison of precision and linear regression values did not reveal any significant diff erences among the allergens used in this study. We conclude that the mRAST methods provide good reproducibility and excellent analytical sensitivity, demonstrating its continued acceptability for use in laboratories performin g routine testing of clinical samples for specific IgE.