RESUMO
BACKGROUND: Sensitization to Blomia tropicalis (Bt) is very frequent in the tropics, and particularly in Cuba, being a significant cause of allergic asthma. Allergen immunotherapy (AIT) with Bt can be a therapeutic option, however, placebo-controlled clinical trials have not been reported. OBJECTIVE: To assess the therapeutic effect and safety of AIT for asthma using a standardized allergen vaccine of B. tropicalis by subcutaneous route, in allergic asthmatic patients exposed and sensitized to this mite species. METHODS: A double-blind, placebo-controlled Phase II trial was conducted in 35 adults (18 with treatment and 17 with placebo), with mild to moderate asthma, predominantly sensitized to Bt. AIT was administered subcutaneously in increasing doses from 4 to 6000 Biological Units using a locally manufactured standardized extract (BIOCEN, Cuba). Patient assessment was performed using symptom-medication score (SMS), peak expiratory flow and skin reactivity relative to Histamine as measured by skin prick test (SPT). RESULTS: The 12-month treatment achieved a significant (p < 0.001) decrease of SMS. Symptom score showed only 41% (CI: 26-61) of placebo values, whereas medication was 34.5% (22.4%-63.3%). Treatment was regarded clinically effective in 67% of patients (OR 32; 95%CI: 17 to 102). The effect size on symptoms and medication was higher than has been reported with equivalent allergen dosages of D. pteronyssinus and D. siboney in Cuban asthmatic patients. Skin reactivity to Bt was also significantly reduced (p = 0.0001), increasing 148-fold the allergen threshold to elicit a positive skin test. This desensitization effect was specific to Bt and did not modify the reactivity to Dermatophagoides. The change of specific skin reactivity was significantly (p < 0.05) correlated to clinical improvement. All adverse events were local with a frequency of 2.4% of injections. CONCLUSIONS: Subcutaneous AIT with Blomia tropicalis was effective and safe in asthmatic adults exposed and sensitized to this mite species in a tropical environment. TRIAL REGISTRATION: Cuban Public Registry of Clinical Trials: RPCEC00000026 (WHO International Clinical Trial Registry Platform ICTRP).
RESUMO
BACKGROUND: There is considerable variability in how allergen extract potency is measured and reported worldwide. In Europe, where many sublingual immunotherapy studies have been conducted, manufacturers report allergen extract potency as units based on an in-house reference, making it difficult to understand the exact doses used and to compare studies. OBJECTIVES: To describe the various methods of expressing extract potency that European allergen extract manufacturers use and to gather reports on the micrograms of major allergen of the in-house units of European allergen extract manufacturers. METHODS: Information was derived from 3 sources: data on extract potency in micrograms of major allergen in articles on sublingual immunotherapy found by PubMed (references through October 2005) and in reference articles, brochures on allergen extracts from the manufacturers, and information provided by structured questionnaires e-mailed to the manufacturers. RESULTS: All but 1 of the European allergen extract manufacturers use in-house reference standards that are based on titrated skin prick testing of allergic patients. Subsequently, in vitro tests compare the potency of commercial batches with the in-house reference and potency is assigned as arbitrary units. Most manufacturers measure major allergen content of their standardized products but do not release this information with the package insert. Diversity in major allergen content was found. CONCLUSIONS: Micrograms of major allergens given in articles on sublingual immunotherapy to express the dose administered cannot be used to translate the dose to US extracts. Extract potency can only be compared if uniform test methods and reference extracts are used.