TRUE GLUCOSE: THE BULLS-EYE AT LAST! CONFIRMATION THAT GLYCERALDEHYDE ADDED TO FLUORIDE IS EFFECTIVE IN PRESERVING BLOOD GLUCOSE IN VITRO B R Muller, Dawn Grenshaw and Rebecca Maddison Clinical Chemistry, Hammersmith Hospitals Trust, Charing Cross Hospital, Fulham Palace Road, LONDON, W6 8RF INTRODUCTION It has long been known that fluoride oxalate fails to adequately preserve glucose in whole blood. Plasma levels drop by about 0.5 mmol/L and only stabilise after 2-4 hours. WHO guidelines state that whole blood samples for glucose should be centrifuged immediately, which is not always practical. There is, therefore, a need for a more effective way of preserving blood samples for glucose measurement. The addition of glyceraldehyde to fluoride oxalate tubes has recently been reported to improve glucose preservation, and in this study we have tested this suggestion in a clinical setting. Mean glucose values in standard and glyceraldehyde treated tubes compared to stat-spun samples Routine () and Glyceraldehyde () Glucose vs. Stat-Spun Glucose. METHODS Blood collection tubes were prepared the day before use by freeze-drying glyceraldehyde to the inside walls of fluoride oxalate vacutainer tubes. 89 patients attending out-patient phlebotomy were recruited over an 8 week period, and three blood glucose samples were collected from each. A standard fluoride oxalate tube was centrifuged within 3 minutes, while a second standard fluoride oxalate tube and a glyceraldehyde treated tube were sent to the laboratory by the usual transport, times to centrifugation ranging from 43-435 minutes (median 144 minutes). All samples were analysed on the day of collection on an Olympus AU640 analyser. CONCLUSION This study confirms the failure of fluoride oxalate to preserve glucose in whole blood, but strongly supports the suggestion that a combination of fluoride and glyceraldehyde is a highly effective preservative. RESULTS Routine fluoride oxalate samples were on average 0.49 mmol/L lower than the samples centrifuged immediately. However, there was no signicant difference between the glyceraldehyde treated samples and the stat-spun samples, demonstrating that the addition of glyceraldehyde to fluoride oxalate tubes dramatically improves glucose preservation.