Immunoradiometric assay for alpha gamma- and gamma gamma-enolase (neuron-specific enolase), with use of monoclonal antibodies and magnetizable polymer particles.

Monoclonal antibodies were raised against neuron-specific enolase, gamma gamma-enolase, and used in an immunoradiometric assay (IRMA), with mono-disperse magnetizable particles as the solid phase. The assay's sensitivity was 0.4 microgram/L and the interassay coefficient of variation was less than 5% in the working range from 0.4 to 170 micrograms/L. Compared with our radioimmunoassay based on polyclonal antibodies, the incubation time is shorter, and precision and sensitivity are improved. The IRMA also improved detection of neuron-specific enolase in sera from patients with lung cancer without a concomitant change in measured enolase in the reference population. The better sensitivity of the IRMA results from its ability to measure alpha gamma- and gamma gamma-enolase with equal response. Ninety percent of the small-cell lung carcinoma patients (36 of 40) had increased values before treatment, compared with 7% of non-small-cell lung carcinoma patients (8 of 114).