Biological variation of serum neuron-specific enolase and carbohydrate antigen 724 tumor markers

BACKGROUND: The aim of our study was to assess two tumor markers, carbohydrate antigen 724 (CA724) and neuron-specific enolase (NSE), in 20 healthy individuals. Then, we determined their average intra- and inter-individual biological variations (CVI and CVG ). METHODS: Blood samples were taken at weekly intervals for five weeks from 20 healthy subjects through a detailed questionnaire and physical examination. These samples were stored at -80°C and analyzed in a single run in duplicate. We calculated the biological variations, the reference change value (RCV), and the index of individuality (II) for the two tumor markers. RESULTS: The intra-individual and inter-individual biological variations were 50.3% and 103.4% for CA724, and 10.1% and 12.0% for NSE, respectively. The II values for CA724 and NSE were 0.48 and 0.85, respectively. CONCLUSION: We determined the biological variations and indices of individuality for CA724 and NSE among 20 healthy subjects. These results will improve clinical applications of the markers.