Effects of summer mailing on in vivo and in vitro relative potencies of standardized timothy grass extract

Background: Allergen extracts can degrade when exposed to temperatures significantly beyond the optimum storage recommendation of 4°C. Many allergen extracts are mailed to their final destinations throughout the year with exposure to varied environmental conditions. Objective: To evaluate the effect of summer mailing on the in vitro and in vivo potency of timothy grass extract. Methods: Standardized timothy grass extracts, 10,000 and 100,000 BAU/mL, were mailed round-trip between San Antonio, Texas, and Phoenix, Arizona, during August 2007. In-transit temperatures were recorded using a portable temperature logger. After mailing of the extracts, we performed quantitative in vitro enzyme-linked immunosorbent assay inhibition and in vivo ID ₅₀EAL (Intradermal Dilution for 50-mm Sum of Erythema Determines Bioequivalent Allergy Units) analysis. Results: Measured extract exposure temperatures were greater than 20°C for 11 days and 30°C for 6 hours during standard mailing in weather temperatures exceeding 38°C. Enzyme-linked immunosorbent assay inhibition results for the 100,000- and 10,000-BAU/mL control samples were 97,900 and 10,580 BAU/mL, respectively, and for the mailed extracts were 96,800 and 7,830 BAU/mL, respectively. These measurements fell within the current Food and Drug Administration lot release limits (67%-149%) and stability limits (50%-200%) relative to the standardized reference. The ID₅₀EAL determinations of the control vs mailed extracts were 12.98 vs 12.28, 12.66 vs 12.32, and 11.97 vs 11.70 for the 3 patients. These differences were not statistically significant. Conclusions: Mailing of timothy grass extract produced no significant reductions in in vitro relative potencies or in vivo skin test reactivity in 3 sensitive patients.