Sedimentation by gravity stabilizes plasma glucose for up to 60 minutes.

Objective: Glucose levels decrease in whole blood in vitro, but there are several methods that minimize the loss, including special tubes and ice. This study evaluated whether sedimentation by gravity in an upright position was a viable alternative.

Design: Lithium heparinized blood was collected from 20 individuals without a diagnosis of diabetes. The samples were allowed to sediment at ambient temperature and were tested in quadruplicate at 30 minute intervals. A Repeated Measures ANOVA compared the means of each time-point.

Results: Plasma glucose results were not statistically different between 30 minutes and 60 minutes after collection (p = 0.156). At 90 minutes after collection, glucose was significantly different than the initial glucose readings (p <0.001). Each reading thereafter also showed a statistically significant difference from the initial reading.

Conclusions: Samples for glucose measurement are stable in lithium heparin for no longer than 60 minutes when held in an upright position prior to centrifugation.