Neurone-specific enolase and Sangtec 100 assays during cardiac surgery: part II - must samples be spun within 30 min?

Sangtec 100 (S-100) (Sangtec Medical, Sweden) and neurone-specific enolase (NSE) assays are showing promise in the assessment of cerebral damage following cardiopulmonary bypass (CBP). The manufacturer's instructions state, however, that samples must be spun and frozen within 30 min, which is inconvenient for serial studies. We, therefore, investigated whether storing blood samples at room temperature (RT) or 4 degrees C for up to 48 h affected the measured levels. Blood samples were taken before and after CBP in six patients and stored for 15 min, 4, 8, 24 or 48 h at RT or 4 degrees C. S-100 and NSE levels did not alter in either 'before surgery' or CPB samples when stored for up to 48 h at 4 degrees C. There was a small, nonsignificant rise when stored at RT. Samples may, therefore, be collected throughout long operations or stored overnight without affecting NSE or S-100 plasma levels.