A solid-phase fluoroimmunoassay for human IgE

A fluoroimmunoassay (FIA) for the measurement of immunoglobulin E (IgE) is described. The method involves a sandwich technique in which antiserum to human IgE is adsorbed on a cellulose acetate/nitrate disc which is attached to a plastic StiQTM sampler. The prepared sampler is reacted with serum and antigen is bound specifically. After buffer wash and treatment with goat serum to block non-specific binding, the samplers are reacted with monospecific fluorescein conjugated antisera to human IgE. Two buffer washes remove unbound material and the fluorescence which is directly proportional to the IgE concentration is measured in a FIAX fluorometer. Assay standards range from 2 to 400 IU/ml. The method gives within run coefficients of variation (CV) from 3.3 to 8.4% and between run CV from 6.2 to 16.1% being less precise at low analyte concentrations. IgE concentrations of a group of 74 sera determined by FIA using StiQsTM prepared with antisera from 2 sources correlated well with results found by radioimmunoassay.