Comparison of histamine release assay and RAST inhibition as tools for allergen extract standardization.

We compared allergen-induced histamine release (HRA) from actively sensitized human leukocytes and RAST inhibition (RI) for their capacity to measure the activity of allergen extracts. Four different grass pollen preparations were investigated for their allergenic activities by employing leukocytes and sera from 13 patients sensitive to grass pollen allergens. We could demonstrate that both test systems detect differences in allergenic activities of the preparations with similar accuracy and reproducibility. HRA is more sensitive than RI but shows greater variability of the results. Pooling of sera from individual patients diminishes individual sensitivities in RI. By this means the precision of RI is further increased. As reagents for RI can be standardized and stored under stable conditions, RI can be performed at different times and different laboratories under identical conditions. For these reasons, RI seems to be more suitable for routine standardization of allergen extracts than HRA.