Brief report: evaluation of polymerized ragweed extracts by intradermal end point titration, RAST inhibition, and parallel line bioassay.

We have evaluated six polymerized ragweed extracts on the basis of RAST inhibition, parallel line bioassay, and intradermal end point titration. The results of the parallel line bioassay and intradermal end point titration are highly correlated (r = 0.995, df = 2, p less than 0.01). Both intradermal end point titration (r = 0.973, df = 4, p less than 0.01) and parallel line bioassay (r = 0.985, df = 2, p less than 0.05) are highly correlated with RAST inhibition. We have evaluated the utility of intradermal end point titration as a quantitative assay of relative allergenicity of polymerized extracts. The between assay reproducibility was derived by comparing a reference polymerized ragweed extract against itself. The 99% confidence limits of relative allergenicity were 53% to 188% when four assays were used. This compares favorably to the published 99% confidence limits of the parallel line bioassay 60% to 166% when three assays were used. Intradermal end point titration is highly reproducible, is highly correlated with RAST inhibition or parallel line bioassay, and thus is an appropriate bioassay of allergenic activity.