Five days serum glucose stability at room-temperature in centrifuged fast-clotting serum tubes and the comparability with glucose in heparin-plasma and plasma containing citrate-stabilizer.

Glucose measurement plays a central role in the diagnosis of gestational diabetes mellitus (GDM). Because of earlier reports of overestimation of glucose in the widely used tubes containing granulated glycolysis inhibitor, the study assessed the performance of fast-clotting serum tubes as an alternative sample for the measurement of glucose. Glucose concentration in fast-clotting serum was compared to lithium-heparin plasma placed in an ice-water slurry after sample collection and glucose stability at room-temperature was studied. Blood samples from 30 volunteers were drawn in four different types of tubes (serum separator tubes, fast-clotting serum tubes, lithium-heparin tubes and sodium fluoride, EDTA and a citrate buffer (NaF-EDTA-citrate) tubes, all from Greiner Bio-One). Lithium-heparin tubes were placed in an ice-water slurry until centrifugation in accordance with international recommendations and centrifuged within 10 min. After centrifugation, glucose was measured in all tubes (timepoint T₀) and after 24, 48, 72, 96 and 120 h of storage at 20-22 °C. NaF-EDTA-citrate plasma showed significant overestimation of glucose concentration by 4.7% compared to lithium-heparin plasma; fast-clotting serum showed glucose concentrations clinically equivalent to lithium-heparin plasma. In fast-clotting serum tubes, mean bias between glucose concentration after 24, 48, 72, 96 and 120 h and T₀ was less than 2.4%. All individual differences compared to T₀ were less than 6.5%. The results fulfill the acceptance criteria for sample stability based on biological variation. Fast-clotting serum tubes can be an alternative for the measurement of glucose in diagnosis and management of GDM and diabetes mellitus, especially when prolonged transportation is necessary.