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November 19, 1982

Potency of Ragweed Extracts

JAMA. 1982;248(19):2449. doi:10.1001/jama.1982.03330190019011

To the Editor.—  In response to the news items covering our presentation at the American Academy of Allergy and Immunology (1982;247:2203), there are several points that we believe need clarification. The major inaccuracy concerns the statement that the simple variable of refrigeration correlated with the potency of extracts studied. This was not the case. While others1-3 have demonstrated a loss of extract potency that depends on storage time and temperature, we were unable to find such a correlation. The fact that we were unable to demonstrate such a correlation may be because of the relatively small number of extracts studied or the multiple variables involved.Although we did show a substantial degree of variability in skin test reactivity and antigen-E (AgE) content, we believe that some explanation of the methods needs to be given. The potency of the skin tests was determined using our adaptation of a method proposed