Characterization and comparison of commercially available mite extracts for in vivo diagnosis

Assessment of sensitization by allergen-specific IgE testing and skin prick testing (SPT) are primary tools in routine clinical diagnosis of allergies. To perform a correct diagnosis, it is critical that the allergen reagent used contains an adequate amount of all relevant components. This study aimed at evaluating commercially available mite extracts for in vivo diagnosis from eight manufacturers.

Eight extracts from Dermatophagoides pteronyssinus and eight from Dermatophagoides farinae were analysed for total protein content by Bradford and for major allergen content by ELISA. SDS-PAGE, immunoblotting and SPT were also carried out.

The protein amount ranged from 27.7 microg/ml extract to 361.1 microg/ml (D. pteronyssinus) and from 20.3 to 353.0 microg/ml (D. farinae). In regards major allergen concentration, Der p 1 ranged from 9.6 to 36.2 microg/ml, Der f 1 26.5-196.1 microg/ml, mite group 2 0.7-31.7 microg/ml in D. pteronyssinus and 1.3-10.4 microg/ml in D. farinae. SDS-PAGE experiments showed that some components are poorly represented or absent in extracts from most manufacturers. Similar results were obtained by IgE-immunoblotting and SPT with 10 mite allergic patients confirmed a broad spectrum of reactivity of the extracts in the same subject.

Immunochemical analysis showed a heterogeneous amount of component/s among mite extracts from different manufacturers. These data were confirmed by in vivo testing, suggesting that, for some of the patient tested, the absence of relevant allergens could strongly affect the diagnosis.