Preparation of a Quality Sample: Effect of Centrifugation Time on Stat Clinical Chemistry Testing

Centrifugation time is a major bottleneck in laboratory specimen throughput. In most cases, 10 minutes is suggested to centrifuge samples on a swing-out rotor centrifuge, at room temperature, with a relative centrifugal force of 1,200±100 g; and 1,300 g or centrifugation times longer than 10 to 15 minutes may be advisable to get a better platelet clearance. Nevertheless, there is little evidence supporting the influence of different centrifuge times for primary lithium-heparin tubes with plasma separator on stat clinical chemistry testing. Five evacuated tubes collected from 10 consecutive subjects were centrifuged on an identical swing bucket centrifuge at 1,200 g for 1, 2, 5, 10, and 15 minutes respectively and tested for clinical chemistry stat analytes. Statistically significant variations from the 15-minute centrifuge reference specimen were observed for ALT, calcium, glucose, potassium, urea nitrogen, and CK-MB (1 minute centrifugation), ALT, glucose, urea nitrogen, and CK-MB (2 minutes centrifugation), and glucose (5 and 10 minutes centrifugation). Meaningful biases according to the analytical quality specifications for clinically-allowable variance were recorded for ALT, calcium, glucose, potassium (1 minute centrifugation), and for ALT, glucose, and potassium (2 minutes centrifugation). We confirm that a 10-minute centrifugation time at 1,200 g on a swing bucket centrifuge for samples collected in plastic tubes with a plasma separator may be suitable for stat clinical chemistry testing.