PubMed1975
The biological activity in the allergic patient is our first and most relevant concern. The physician using an extract must know the quality and degree of allergenic activity in the material. Preferably, it should also be possible for the physician to control such activity by simple techniques. No single test can fully satisfy these demands. The standardization which comes nearest to this is assessment of the biological activity and specificity by means of skin testing using histamine as a reference. Skin testing is, however, limited as regards precision and reproducibility. A more precise standardization may be achieved by means of certain in vitro methods. Relevant in vitro methods are suitable complements to the bio-assay. However, the in vitro methods chosen must be standardized themselves as compared to a stable reference, and their correlation with the biological reactions in man must be established before they can be introduced as possible means for extract standardization. Even then, bio-assays are necessary for control of content of irritants which may elicit non-immunological (non-specific) reactions in the hyperreactive tissues of allergic individuals. Methods for standardization are discussed. Examples of quality gradings of allergen extracts are given with emphasis on minimal requirements to be fulfilled by extracts in order to be accepted for clinical use.