Q:

7/31/2013
I have a patient who was transferring her shot from Germany to us in California. We need to recreate her shot. Her shot is simple, only DP and DF in 1:1 composition. But in Germany they used 10,000 TU/ml. I wonder if it is the same as our DP and DF in 10,000 AU/ml. Is TU in Germany same as AU in US? Thank you in advance!

A:

Thank you for your inquiry.

No, the allergen standardization used in Germany expressed in TU (therapeutic units) is in no way equivalent to the AU designation used for standardization of allergy extracts used in the U.S.. Therefore, unfortunately, you will not be able to make an accurate comparison of potency based upon the TU/ml designation. In addition, there may be other differences since in Europe, they use tyrosine-based vaccines, and the potency of these vaccines are also expressed in TU.

I have copied references and abstracts below that deal with the comparison between European and the United States standardization methods should you wish to read about them further, but the bottom line is that you cannot draw conclusions based upon the therapeutic units in your patient’s vaccine that will allow you to construct a vaccine of similar potency.

WAO Journal Allergen Standardization and Characterization
Posted: September 2009

Therapeutic units (tu/ml). the unitage is based on the biological activity of the allergen extract

Ann Allergy Asthma Immunol. 2008 Feb;100(2):137-45. doi: 10.1016/S1081-1206(10)60422-X.
European allergen extract units and potency: review of available information.
Larenas-Linnemann D, Cox LS; Immunotherapy and Allergy Diagnostics Committee of the American Academy of Allergy, Asthma and Immunology.
Source
Hospital Médica Sur, Mexico City, Mexico.
Abstract
Background: There is considerable variability in how allergen extract potency is measured and reported worldwide. In Europe, where many sublingual immunotherapy studies have been conducted, manufacturers report allergen extract potency as units based on an in-house reference, making it difficult to understand the exact doses used and to compare studies.
Objectives: To describe the various methods of expressing extract potency that European allergen extract manufacturers use and to gather reports on the micrograms of major allergen of the in-house units of European allergen extract manufacturers.
Methods: Information was derived from 3 sources: data on extract potency in micrograms of major allergen in articles on sublingual immunotherapy found by PubMed (references through October 2005) and in reference articles, brochures on allergen extracts from the manufacturers, and information provided by structured questionnaires e-mailed to the manufacturers.
Results: All but 1 of the European allergen extract manufacturers use in-house reference standards that are based on titrated skin prick testing of allergic patients. Subsequently, in vitro tests compare the potency of commercial batches with the in-house reference and potency is assigned as arbitrary units. Most manufacturers measure major allergen content of their standardized products but do not release this information with the package insert. Diversity in major allergen content was found.
Conclusions: Micrograms of major allergens given in articles on sublingual immunotherapy to express the dose administered cannot be used to translate the dose to US extracts. Extract potency can only be compared if uniform test methods and reference extracts are used.

Thank you again for your inquiry and we hope this response is helpful to you.

Sincerely,
Phil Lieberman, M.D.

AAAAI - American Academy of Allergy Asthma & Immunology