Acidification of Blood Is Superior to Sodium Fluoride Alone as an Inhibitor of Glycolysis

Abstract

Acidification should replace NaF alone as the recommended method for obtaining an accurate glucose concentration. Diagnostic cut points based on blood samples collected into tubes containing NaF as the only inhibitor of glycolysis are likely to be too low.

Inhibition of Glycolysis for Glucose Estimation in Plasma: Recent Guidelines and their Implications

“…The mean glucose concentration decreased by 0.3 % at 2 h and by 1.2 % at 24 h when blood was drawn into citrate buffer tubes. In contrast, the mean glucose concentration decreased by 4.6 % at 2 h and by 7.0 % at 24 h when blood was drawn into sodium fluoride tube [6]. In another recent study reported from Spain, 70 paired samples were processed for glucose in three different sets of pre analytical conditions.…”

“…These ingredients are a granular mixture of a citrate buffer, sodium fluoride and disodium EDTA with a combined mass of 7.5 g/L of blood. The tube is not available worldwide and currently being used in Europe [6].…”

“…The requirement that serum samples must be allowed to clot before serum glucose is tested significantly increases turnaround time for glucose results compared with plasma results [11]. There is also some suggestion that clotting consumes glucose [6]. Therefore, serum glucose concentrations will always be lower than plasma glucose if glycolysis in a plasma sample is inhibited immediately.…”

“…The amount of the difference will vary with the glycolysis rate in the individual specimen and the time elapsed between collection and centrifugation [4]. The comparison of paired blood samples for serum & heparinized plasma collected and stored at same ambient temperature and centrifuged at same time produced higher glucose values in plasma [6]. On the other hand studies comparing the results of serum gel separator tubes with those of fluoride tubes have reported higher glucose values in serum samples [3,4,12].…”

“…Mechanisms can be developed to either centrifuge the glucose samples immediately in the sample collection area and transport to central lab on ice packs or they can be directly sent to laboratory on priority basis immersed in ice slurry, where immediate processing could take place. Moreover heparin tubes are available in which, glucose levels measured after immediate centrifugation has been used as the reference concentration to compare the results in various studies [6,7]. Meanwhile efforts should be made to make citrate buffer tubes available worldwide or develop collection tubes with similar anti glycolytic action.…”