A method for quantitation of food biologic activity: results with peach allergen extracts.

OBJECTIVE: The aim of this study was to develop a quantitative skin test assay for measurement of the biologic activity of food allergen extracts, as well as to report the results obtained with a peach extract labeled in food biological units (FBUs).
METHODS: We prepared a biologically quantified peach extract. The biologic activity was measured in FBUs by assigning 100 FBU/ml to the biologic activity of the extract that elicited a wheal area with a geometric mean equal to that produced by the prick-prick method by using the food itself in a population of 30 patients allergic to food. We evaluated 265 patients, including 70 patients allergic to peach and 195 control subjects (100 nonatopic subjects and 95 subjects allergic to pollen). The biologically quantified peach extract was used during the study and was compared with four commercial peach extracts, which were labeled in weight per volume.
RESULTS: The sensitivity of the nonstandardized commercial peach extracts varied from 4.3% to 74%, with biologic activity being very low in all of them. The sensitivity of the biologically quantified peach extract was 100%, with a 100% concordance between the prick-prick and the skin prick test results.
CONCLUSION: These data demonstrate that if peach allergen preparations were biologically standardized in FBUs, the quality of these food extracts used for diagnosis would be improved.