[Importance of hemolysis on neuron-specific enolase measurement].

The aim of this work is to establish a pre-analytical approach suitable for the neuron-specific enolase (NSE) measurement. This enzyme which is synthesized by neurons and neuroendocrine cells, is a marker useful for the diagnosis and the monitoring of patients with neuroendocrine tumors (neuroblastoma, small cell lung cancer) and during stroke to assess neuronal damage. This NSE measurement is very sensitive to hemolysis due to the abundance of the enzyme in red blood cells. Two methods of evaluation of hemolysis have been compared: the determination of free haemoglobin (Hb) by spectrophotometry and the indirect measurement of an hemolytic index with a multiparameter analyzer, the Modular (Roche Diagnostics). The correlation between these 2 methods on 42 samples is very satisfactory: Y (free Hb) = 12.337 X (index) + 31.743 r = 0.997. The NSE assay is based on TRACE (Time Resolved Amplified Cryptate Emission) technology, on a Kryptor (BRAHMS). The influence of hemolysis on the determination of NSE was confirmed by overloading with hemoglobin (hemolysate) 3 pools of serum with NSE concentrations close to the threeshold decision. The determination of NSE shows an increase in concentration parallely to the hemolytic index (about 150% for an hemolytic index of 10). Consequently, in our laboratory the NSE determination is realized only for samples presenting an hemolytic index < or = 10, this allowing a good monitoring of kinetics of this marker.