Which sample tube should be used for routine glucose determination ?

tBackground: Glucose is one of the most frequently requested analytes in clinical laboratory.Blood glucose analysis is affected from in vitro glycolysis. In order to determine the mostsuitable blood collection tube for this purpose we have compared different tubes: sodiumfluoride, lithium heparin, sodium fluoride/citrate buffer containing tubes and serum withclot activator tube for the measurement of glucose when the tube has been kept at roomtemperature (RT) for up to 4 h.Methods: Venous blood was collected from 49 healthy volunteers into Sarstedt S-Monovettesfor glucose analysis. Reference plasma glucose was determined in a lithium heparin tubeand immediately placed in an ice/water slurry. Within 10 min it was centrifuged at 4◦C andplasma was separated from the blood cells. Samples have been preserved at RT for 1, 2 and4 h after drawing. Glucose has been determined using a hexokinase method.Results: Glucose levels tested in a serum with clot activator tube, in lithium heparin andin sodium fluoride/sodium EDTA tubes when compared with lithium-heparin referenceplasma did not meet the desirable bias for glucose (±1.8%) when kept at RT for up to 4 h.GlucoEXACT tubes, when corrected by the Sarsted recommended factor of 1.16, showed amean (95% CI) bias of +0.96% (0.45–1.47) at 1 h, +1.40% (0.88–1.93) at 2 h and +0.95% (0.44–1.46)at 4 h, reaching the analytical goal for the desirable bias.Conclusions: Samples collected into GlucoEXACT tubes containing sodium fluoride/citratebuffer liquid mixture are equivalent to those collected in reference plasma tubes avoidingglycolysis completely and within a 4 h delay in plasma separation.