Laura Boyle¹, Richard Ruddell¹

¹Chemical Pathology, John Hunter Hospital, New Lambton Heights, NSW, Australia

 

Introduction:  Neuron specific enolase (NSE) is a tumour marker used to monitor neuroendocrine tumours including small-cell lung carcinoma. However, the gamma isoform of NSE is released from erythrocytes during haemolysis, leading to false elevation of results. While the manufacturer advises to exclude haemolysed specimens from analysis, haemolysis can occur even during ideal venepuncture conditions.  Seeking a practical solution, an experimental protocol was developed to determine the index at which the impact of haemolysis becomes analytically and clinically significant.

Method: Lysate generated from freeze-thaw cycles of the plasma of healthy volunteers was spiked into pooled plasma and pooled serum to generate 5% stock solutions. Serial dilution was then conducted to produce aliquots with increasing lysate percentages. 

Discussion: The HI and NSE values were calculated for each aliquot and regression analysis was performed to derive an expected increase of 30 +/- 1 ng/mL in NSE per increase in 1 unit of haemolysis (g/L). This value was applied to the RCPA analytical specifications for NSE, the within-subject biological variation for NSE and our assay’s analytical imprecision to generate haemolysis index limits at which to automatically validate the result, validate with a comment or refer for pathologist review in keeping with CLSI guidelines.