After the pollen used for the production of allergenic extracts has been collected, their identity and purity must be evaluated. Microscopic analysis is performed for this purpose. Currently, pollen purity assessments include counting and identifying biological components contaminating the pollen. However, this method of evaluating pollen purity does not consider either the potential clinical relevance of specific contaminants or their relative volume compared to that of the pollen in the final sample. While the potential clinical relevance of many pollen contaminants is unknown, volumetric counting instead of particle counting could provide a better estimation of the amount of foreign biological materials contained in pollen. However, standardized and approved methods to perform this evaluation are lacking.
For the purpose of microscopic pollen identity and purity evaluations, samples are stained with a solution and examined under various magnifications. Microscopic pollen analysis also can provide valuable information regarding pollen quality for the production of pollen extracts. For example, the presence of a large number of plant parts and a variety of miscellaneous fungal spores generally indicates that the pollen is not sufficiently clean, and that additional activities to remove biological contaminants are necessary. To the contrary, the presence of large amounts of one single spore type, hyphae, and/or sporulating structure indicates that fungi have actively infested the pollen for a period. This pollen should be discarded for the production of pollen extracts.
Qualified individuals should perform the pollen identification and purity assessments in appropriate in-house laboratories at allergen manufacturing companies. However, programs to train individuals and certify such laboratories are currently lacking.
It is essential to perform all activities associated with pollen used for the production of pollen extracts, including identification and purity assessments, in dedicated areas of allergen manufacturing companies where other types of raw materials are not present. Otherwise, cross-contamination of pollen used to produce pollen extracts with other allergenic products will likely occur.