Performance characteristics of immunoenzymatic allergosorbent testing for total and specific immunoglobulin E

Paper disc-based solid phase radioimmunoassays are widely used in vitro diagnostic test kits for measuring total IgE (Phadebas PRIST) and specific IgE antibodies (RAST). Recently, these kits have been modified by the substitution of an enzyme-linked immunosorbent assay detection system (Phadezym PRIST/RAST). We studied the performance characteristics of Phadezym PRIST and RAST kits. Phadezym PRIST was sensitive to 0.5 IU/mL IgE. Reproducibility was excellent in the range of 5 to 200 IU/mL IgE and adequate in the range of 5 to 1000 IU/mL using 1:10 serum dilutions (average inter-assay coefficient of variation = 19%). Phadezym RAST was specific, but sensitivity was limited by absorbances in the RAST class 1/0 range indistinguishable from background values. Average inter-assay coefficient of variation was 29% for the semi-quantitative 'Phadezym RAST Unit' (PRU) reporting system. We modified the test kit procedure by disc incubations in microtiter plate wells with rotational agitation and use of ELISA-dedicated spectrophotometer and computer software. These microplate accelerated computerized assays ('MacPRIST' and 'MacRAST') were shown to perform similarly to the conventional Phadezym procedures with advantages in speed, ease, and handling of data.