Development of a new automated enzyme immunoassay for the determination of neuron-specific enolase.

Neuron-specific enolase (NSE) represents the gamma gamma- and alpha gamma- isoforms of the dimeric glycolytic enzyme enolase. NSE is predominantly found in neurons and neuroendocrine cells and has proven to be a marker for tumors derived from these cells. It is widely accepted in the monitoring of patients with small cell lung cancer and is also of value as an aid in diagnosis. Recently it has become of interest in the monitoring of brain damage. Monoclonal antibodies against gamma-enolase were raised in mice and selected for optimal performance on the Cobas Core enzyme immunoassay system. The antibody combination of choice was MAb 18E5 for capturing and MAb 84B10 for detection which is accomplished by using a horseradish peroxidase conjugate and the substrate 3,3',5,5'-tetramethylbenzidine. The resulting assay is a one-step enzyme immunoassay of the sandwich type. It is performed on the fully automated Cobas Core immunoassay analyzer with a total assay time of 45 min. The sample volume is 10 microliters. Calibration is done by a 1-point recalibration using a lot-specific master calibration curve provided with the kit. The dynamic range is 0-200 ng/ml. The analytical detection limit (standard 0 + 2SD) of the Cobas Core NSE EIA II was 0.1 ng/ml. Intra- and interassay coefficients of variation were < 5% and < 6%, respectively. A Hook Effect was not observed up to a concentration of 20'000 ng/ml. Test results correlated closely with the well established polyclonal Cobas Core NSE EIA (r = 0.99). In summary, the Cobas Core NSE EIA II is a rapid, reliable and convenient test for measuring NSE in human serum.