Neurone-specific enolase and Sangtec 100 assays during cardiac surgery: part III - does haemolysis affect their accuracy?

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Abstract
Neurone-specific enolase (NSE) and Sangtec 100 (S-100) are useful for detecting cerebral damage during cardiopulmonary bypass (CPB). However, red cells contain NSE, and the haemolysis frequently caused by CPB could produce a false rise in NSE; S-100 is not found in red cells and should not be affected. We, therefore, compared the effects of haemolysis on NSE and S-100 to see if correction was necessary and possible. From seven patients, serial dilutions of haemolysed red cells were added to plasma (1/64-1/2048), measured for absorption at 540 nm and assayed for NSE and S-100. S-100 concentrations showed no change with haemolysis. Measured NSE increased significantly with haemolysis >1/512 (an increase of 6.6 μg/ml): a correction formula is presented. In 39/48 patients after CPB, mean haemolysis was <1/256 and would not need any correction. NSE and S-100 assay can, therefore, be used throughout CPB, which allows both glial and neuronal damage to be studied.