A comparison of in vitro potency between European and Mexican allergen extracts and US (CBER/FDA) reference extracts.

BACKGROUND The most important allergen manufacturers are based in Europe and in the US. In some countries local products are also sold. No comparison between European, US and local products has been made until now. AIM OF THE STUDY To determine total protein content and total specific IgE binding capacity or major allergen content of diagnostic extracts from European, US and Mexican origins relative to the CBER/FDA reference extracts for Dermatophagoides pteronyssinus (Dpt), Bermuda grass and cat (10,000(B) AU/mL). METHODS Diagnostic extracts were purchased from various manufacturers, blinded and shipped to the analysing laboratory, where the following assays were conducted: total protein concentration (Bradford), specific IgE competition ELISA (Dpt and Bermuda grass) and determination of Fel d 1 U/mL. When available, CBER/FDA recommended tests and reagents were used. RESULTS Total protein content of US reference extracts was higher than all other extracts. Relative potency of European and US-bought Dpt extracts 3,300-4,400 AU/mL, Bermuda grass 800-2,500 BAU/mL and cat 2.1-4.4 Fel d IU/mL (Ref. 19 U/mL), with one exception. Locally produced Mexican products were almost all below 1,000 (B)AU/mL. CONCLUSIONS Three diagnostic extracts from European manufacturers and from Mexican providers which obtain extracts in US have a <50% relative potency compared to 10,000 (B)AU/mL US extracts. Locally produced Mexican extracts have much lower total protein content and specific IgE binding capacity. These in vitro results must be complemented with other in vitro and in vivo skin prick tests to obtain a more complete picture of comparison of potency. Nevertheless results are quite consistent for the allergens tested here.