The biologic strength (potency) of an allergenic extract can be expressed in a variety of ways. In general, all allergenic extracts are divided into 2 categories:
The FDA has mandated standardization testing for a limited number of extracts. The purpose of standardization is to minimize the amount of variability between lots and manufacturers of the same extract.
Non-standardized (w/v or PNU)
Allergenic extracts that are considered non-standardized do not undergo additional laboratory testing to verify relative biologic strength. Instead, non-standardized extracts are assigned potency values based on either the product’s extraction ratio (source material-to-extracting solution) or on an estimated measure of total protein.
Within each of these categories, Major Allergen concentration is a variable that can provide additional information about an extract's potency.