Radioimmunoassay development for human neuron-specific enolase: with some clinical results in lung cancers and neuroblastoma.

: A double-antibody radioimmunoassay for human neuron-specific enolase (NSE) was developed, using rabbit antiserum against the gamma subunit of enolase purified from human brain. Intra-assay variance was 3.8-5.1% and inter-assay variance 4.3-7.3%, and recovery of NSE added to normal serum was 100.2% on average. Normal serum NSE levels for 451 adults ranged from 3.6 to 10.8 ng/ml (mean 6.6 ng/ml). Antibodies raised against the gamma gamma enolase isozyme did not cross-react with the alpha alpha and beta beta isozymes at concentrations of 1,000 ng/ml, but showed a cross-reactivity of 41.5% (theoretically 50%) with the alpha gamma isozyme. It was also shown that hemolysis of 160 mg/dl hemoglobin can add 5.73 ng/ml of NSE to the true level. The coefficient of correlation between the radioimmunoassay and the sandwich enzyme immunoassay [1] was 0.99 (n = 21), and values determined by the RIA were about twice those obtained by the EIA. Serum NSE was abnormally high in 42 of 52 patients (80.8%) with small cell lung carcinoma, and in all 38 children with neuroblastoma.