Influence of centrifugation conditions on the results of 77 routine clinical chemistry analytes using standard vacuum blood collection tubes and the new BD-Barricor tubes

Abstract

Introduction: Although centrifugation is performed in almost every blood sample, recommendations on duration and g-force are heterogeneous and mostly based on expert opinions. In order to unify this step in a fully automated laboratory, we aimed to evaluate different centrifugation settings and their influence on the results of routine clinical chemistry analytes.

Materials and methods: We collected blood from 41 healthy volunteers into BD Vacutainer PST II-heparin-gel- (LiHepGel), BD Vacutainer SST II-serum-, and BD Vacutainer Barricor heparin-tubes with a mechanical separator (LiHepBar). Tubes were centrifuged at 2000xg for 10 minutes and 3000xg for 7 and 5 minutes, respectively. Subsequently 60 and 21 clinical chemistry analytes were measured in plasma and serum samples, respectively, using a Roche COBAS instrument.

Results: High sensitive Troponin T, pregnancy-associated plasma protein A, ß human chorionic gonadotropin and rheumatoid factor had to be excluded from statistical evaluation as many of the respective results were below the measuring range. Except of free haemoglobin (fHb) measurements, no analyte result was altered by the use of shorter centrifugation times at higher g-forces. Comparing LiHepBar to LiHepGel tubes at different centrifugation setting, we found higher lactate-dehydrogenase (LD) (P = 0.003 to < 0.001) and lower bicarbonate values (P = 0.049 to 0.008) in the latter.

Conclusions: Serum and heparin samples may be centrifuged at higher speed (3000xg) for a shorter amount of time (5 minutes) without alteration of the analytes tested in this study. When using LiHepBar tubes for blood collection, a separate LD reference value might be needed.

Keywords: centrifugation; diagnostic tests; pre-analytics; routine.

Figure 1

Sample collection and preparation workflow.
LiHepGel – vacuum lithium heparin gel tubes. LiHepBar – vacuum lithium heparin Barricor tubes.

Figure 2

Comparison of absolute results of lactate-dehydrogenase (A), bicarbonate (B), free haemoglobin in plasma (C) and serum (D) between centrifugation settings and tube types. Scales on the y-axis represent differences in absolute values of the respective analyte. IDs on the x-axis represent the different centrifugations settings: 1 – LiHepBar 2000xg/10min; 2 – LiHepBar 3000xg/5min; 3 – LiHepGel 2000/10min; 4 – LiHepGel 3000xg/5min; 5 – LiHepGel 3000xg/7min; 6 – Serum 2000xg/10min; 7 – Serum 3000xg/5min; 8 – Serum 3000xg/7min. *P < 0.05; **P < 0.01; ***P < 0.001. P-values < 0.05 were considered statistcally significant.