Measurement of the absolute level of specific IgE to Dermatophagoides farinae by dot radioimmunoassay: relationship between the ratio of specific IgE to total IgE and skin reactivity.

Allergen dot radioimmunoassay (dot-RIA), employing nitrocellulose filter paper (NFP) as the solid phase, and a Phadebas RAST tracer as the detecting antibody was used to measure the absolute amount of specific IgE to Dermatophagoides farinae (D. farinae) in forty-five D. farinae-sensitive patients and ten negative controls. These results with dot-RIA were compared with those with D. farinae radioallergosorbent test (RAST). When the elution of D. farinae-specific IgE from antibody-dotted NFP complex by alkaline buffer (pH 11.0) was done and followed by measurement of IgE contents in various dilutions of eluate to construct a standard curve, D. farinae-RAST exhibited greater binding than dot-RIA. There was a similar high degree of correlation of specific IgE levels between the ratio of specific IgE to total IgE by dot-RIA and RAST when compared with the wheal size on skin prick test to D. farinae. It was suggested that dot-RIA using NFP as the solid phase-a simple, less expensive, and reproducible method-is applicable for measuring the absolute level of specific IgE to D. farinae and for determining the relationship between the ratio of specific IgE to total IgE and the wheal size on skin prick test in D. farinae-sensitive patients.