Sodium fluoride: an ineffective inhibitor of glycolysis.

Entrenched in current laboratory protocols for the measurement of plasma glucose is the false belief that sodium fluoride (NaF) is an effective inhibitor of glycolysis. The failure of NaF to properly control glycolysis decreases plasma glucose concentrations. The amount of the decrease can be clinically significant. The most recent (2011) laboratory guidelines for diagnosis and management of diabetes mellitus, approved by the American Diabetes Association, no longer recommend the use of NaF alone to control glycolysis. If plasma cannot be iced and separated from cells within 30 min of collection, the new guidelines recommend the use of a tube that contains a low pH buffer such as citrate. Proper control of glycolysis will affect current glucose cut-off points, but the exact effect is yet to be defined.