Determination of serum neuron-specific enolase by differential immunocapture.

A new method for the determination of serum neuron-specific enolase is presented. It consists of two steps: first, an immunocapture of gamma-subunit containing isoenzymes by absorption on immobilized anti-gamma antibodies; second, bioluminescence assay of enolase activities in untreated control samples and in the supernates of antibody treated samples. Total and alpha alpha activities are obtained, from which the neuron-specific enolase activity (alpha gamma + gamma gamma) can then be calculated by difference. As compared to the procedures currently in use, the immunocapture method is very rapid (30 min) and is more suitable for small series of determinations as needed in clinical chemistry applications. Reference interval values for serum found by this method agree with published data. When tested with samples from patients suffering from neuroblastoma or small cell lung cancer, it confirms the specific elevations in neuron-specific enolase activity previously described for these cancers, using other analytical approaches.