[Indications and utility of allergen provocation testing]

Specific bronchial provocation tests have been used to confirm diagnosis, as a laboratory model for the study of asthma, and to evaluate the efficacy of immunotherapy with allergen extracts. However, despite the advances achieved in our knowledge of the etiopathogenic mechanisms of asthma, bronchial provocation tests with allergens have certain methodological limitations. These are due to the difficulty of evaluating these tests as regards which markers of inflammation (exhaled nitric oxide, carbon monoxide, etc.) should be investigated and at what points in the chronology of the asthmatic response. The current parameters used to assess respiratory function (FEV1, mainly) do not seem to be the most ideal nor do their percentage reductions, usually established by use, always serve to identify a bronchospastic and inflammatory response. Furthermore, the allergen doses indicated in the various protocols do not mimic natural exposure to these allergens, thus introducing an important bias in the interpretation of the results. In this sense, another and no less important difficulty is the lack of adequate standardization of the characteristics of the allergens used; the development of recombinant allergens may eliminate this obstacle and improve the reproducibility of the tests. In view of the above, the requirement of a positive bronchial provocation test to a specific allergen in the etiological diagnosis of asthma does not seem reasonable nor does it seem reasonable that specific immunotherapy is not indicated if the test is negative or that evaluation of its efficacy lies in a negative result for a previously positive test. This premise does not take into account the fact that bronchial reactivity is subject to variables that are difficult to control (prior natural exposure to the allergen, for example).