Original researchWhich sample tube should be used for routine glucose determination?

- We studied different sample tubes for blood glucose determination.
- NaF alone doesn't inhibit rapidly glycolysis.
- NaF and citrate buffer mixture inhibits in vitro glycolysis for up to 4 h.
- NaF/citrate is necessary for accurate glucose determination and diabetes diagnosis.

BackgroundGlucose 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 most suitable blood collection tube for this purpose we have compared different tubes: sodium fluoride, lithium heparin, sodium fluoride/citrate buffer containing tubes and serum with clot activator tube for the measurement of glucose when the tube has been kept at room temperature (RT) for up to 4 h.MethodsVenous blood was collected from 49 healthy volunteers into Sarstedt S-Monovettes for glucose analysis. Reference plasma glucose was determined in a lithium heparin tube and immediately placed in an ice/water slurry. Within 10 min it was centrifuged at 4 °C and plasma was separated from the blood cells. Samples have been preserved at RT for 1, 2 and 4 h after drawing. Glucose has been determined using a hexokinase method.ResultsGlucose levels tested in a serum with clot activator tube, in lithium heparin and in sodium fluoride/sodium EDTA tubes when compared with lithium-heparin reference plasma 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 a mean (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.ConclusionsSamples collected into GlucoEXACT tubes containing sodium fluoride/citrate buffer liquid mixture are equivalent to those collected in reference plasma tubes avoiding glycolysis completely and within a 4 h delay in plasma separation.