Biologic activity of Dermatophagoides siboney and Blomia tropicalis allergens in exposed and unexposed mite-allergic individuals. Effect of patient selection on the biologic standardization of mite extracts

Background: This study aimed to investigate the influence of patient select ion criteria, i.e., mite-allergic individuals exposed and not exposed to De rmatophagoides siboney and Blomia tropicalis, on the biologic activity of m ite extracts. Determination of the potency of mite extracts in vivo require s selection of patients with a clinical history of mite allergy. In Scandin avia, there are some anamnestic criteria for mite allergy, whereas in the t ropics, where patients are continuously exposed to high levels of mites, se lection of patients with mite allergy by clinical history is difficult. Methods: A total of 210 Cuban asthmatics with continuous symptoms, and 43 S wedes with a clinical history of mite allergy were investigated. Skin prick tests were performed with D. siboney, D. pteronyssinus, D. farinae, B. tro picalis, Acarus sire, Lepidoglyphus destructor, and Tyrophagus putrescentia e extracts. For analysis of the biologic activity of mite extracts Cuban pa tients were divided into four groups: 1) all patients skin-test-positive to mites 2) patients positive to mites, but not to other inhalant allergens 3) patients reacting most to the mite species analyzed 4) patients reactive only to mites and reacting most to the mite species an alyzed. The biologic potency was calculated according to the Nordic Guidelines. Results: Due to cross-reactivity between mites, Swedish mite-sensitive pati ents, with a clear clinical history of mite allergy, but not exposed to D. siboney and B. tropicalis, were more skin reactive to these mites than were Cubans. The estimated potency increased gradually to >200% in group 4. In group 1 Cubans, the reactivity to all mites but B. tropicalis was lower tha n that in mite-sensitive Swedes. Conclusions: According to the influence of patient selection criteria on th e estimation of the potency of mite extracts, the determination of the biol ogic activity of allergenic extracts in subjects without a clear-cut clinic al history should be replaced by new methods when available.