Practicable enzyme immunoassay for neuron-specific enolase in human serum

A practicable sandwich-type enzyme immunoassay for neuron-specific enolase (NSE) in human serum was established by the use of purified antibodies to bovine neuron-specific gamma gamma-enolase. The assay system consisted of polystyrene balls (6.5 mm in diameter) with immobilized antibody F(ab')2 fragments and the same antibody Fab' fragments labeled with beta-D-galactosidase from Escherichia coli. The assay could be performed within a working day. The assay system had a minimum detectable sensitivity of 50 pg per assay tube or 1 microgram per liter of NSE in human serum. The assay did not cross-react with nonspecific alpha alpha-enolase and muscle-specific beta beta-enolase. Coefficients of variation in within-assay and between-assay of serum NSE were less than 10%. Serum NSE values (n = 79) determined with the present method correlated well with those obtained by the previously developed method (correlation coefficient r = 0.96, y = 0.92x - 0.83). Serum NSE concentrations of healthy subjects were less than 5 micrograms per liter and those in sera of patients with small-cell carcinoma of the lung were enhanced.