Predictive Surrogate Markers of Allergy: A By-Product of Recombinant Allergens?

specific IgE assay, correlated the intensity of sensitization to the severity of clinical features. For example, in asthmatic children sensitized to house dust mites, allergy is confirmed when the wheal on prick tests is greater than or equal to 6 mm, and allergy is probable when the wheal is greater than or equal to 5 mm [2] . However, skin prick tests cannot constitute a universal criterion due to variations in the biological potency of allergen extracts between various manufacturers, and sometimes even from the same manufacturer. The validity of skin tests in food allergy has also been demonstrated [3] , particularly in terms of sensitivity and negative predictive value. According to Sampson and Ho [3] , a specific IgE assay is also predictive of clinical reactivity during double-blind, placebo-controlled food challenge with cutoffs identified for egg, cow’s milk, peanut and fish. The evidence is so strong that the use of these challenge tests in this setting raises ethical and medical responsibility issues. More recently, the intensity of sensitization, assessed by wheal diameter on skin tests and by specific IgE levels, has been shown to be a predictive factor for subsequent acquisition of immune tolerance in cow’s milk protein allergy [4] . The development of recombinant allergens now makes possible a much more precise identification of the pollens responsible. For example, in tree pollen allergy, and in patients with positive skin tests for birch and ash, the For many years, allergy research has been trying to identify predictive markers of clinical reactivity in order to distinguish between simple biological sensitization and true clinical disease due to allergy. Evidence of true allergic disease is not always available and challenge tests are not sufficiently used. Another important issue is how to determine which patients are candidates for immunotherapy. As polysensitization is a fairly common phenomenon, which allergens should be used for immunotherapy? Can the short-term and long-term success of this treatment be predicted? What are the risk factors for progression of allergy towards a more severe form, such as progression from rhinitis to asthma? Is it possible to identify patients at high risk of serious anaphylactic reactions during immunotherapy? Progress in biology, and especially the availability of very good-quality recombinant allergens, now provides a clearer understanding of allergic diseases. A particularly important contribution was provided by the study by Pastorello et al. [1] in the International Archives of Allergy Immunology , which described, in a large series of patients, the severity of allergic reactions according to the type of sensitizations in a context of pollen-food crossreactivity. In the somewhat distant past, in vivo diagnostic tests, such as prick tests, or in vitro diagnostic tests, such as Published online: August 9, 2011