The use of standardized extracts in allergen immunotherapy

Double-blind, placebo-controlled studies have established that injection allergen immunotherapy is clinically effective. However, it is not known to what extent the doses of allergen extract commonly used in clinical practice match those that have been used in these controlled studies.

The aim of this study was to determine by questionnaire the doses of standardized allergen extracts commonly used by board-certified allergists in the United States and to compare these with doses that have proven effective in double-blind, placebo-controlled studies.

A questionnaire containing a hypothetical case and asking for a recommended allergen prescription for maintenance immunotherapy was mailed to 500 randomly selected board-certified members of the American Academy of Allergy, Asthma and Immunology living in the United States. The recommended doses were compared with those doses of the extracts that had been proven effective by using major allergen content figures for representative standardized US allergen extracts provided by an allergy extract laboratory.

Responses were received from 118 (23%) of the addressees. Eighty (16%) contained interpretable data on maintenance dosing for extracts. The median doses of pollen recommended were comparable with those that have been demonstrated to be clinically effective. Median doses of house dust mites were only slightly lower than those that have proven effective. Median doses of animal dander, on the other hand, were well below those used effectively in controlled studies. Although the median doses used were often in the range of proven doses, the range of doses recommended by allergists included some that were one tenth to one five hundredth those of the median doses.

In the absence of useful guidance from the federal regulatory authorities, American allergists, for the most part, use doses of pollens and house dust mites that are within the proven range. Their dosing of animal dander is generally below proven effective doses. There is, however, a wide range of dosing of all extracts used, and there is use of mixes that have no botanical basis. Therefore there is need for studies defining what are effective and ineffective allergen extract doses.