Introduction: Laboratories commonly collect samples for glucose measurement in sodium fluoride (FL) at room temperature (RT) despite guidelines stating this is insufficient to control in vitro glycolysis. Instead, blood should be immediately placed on ice then separated, or a rapid inhibitor such as citrate buffer (CIT), used. We investigated the potential difference in rates of diagnosis of diabetes mellitus (DM) by oral glucose tolerance test (OGTT) between these collection protocols.
Method: Blood was collected from volunteers in CIT, FL (on ice and at RT) and in serum, and glucose measured at different time-points. The average difference in glucose from CIT was used to retrospectively 're-calculate' 2 years of OGTTs results; all collected in FL at RT and unspun for 2 hours.
Results and discussion: Average differences in glucose at 2 h from CIT were 22.4% (serum), 18.3% (FL at RT) and 7% (FL on ice). After 'adjusting' our OGTT results, the rate of DM increased from 6% to 13.9% (non-pregnant) and from 12% to 37% (pregnant). Although the magnitude of the findings are theoretical, they do suggest that correct collection for glucose is a significant pre-analytical variable.
(C) 2015 Royal College of Pathologists of Australasia