J Clin Pathol 62:752-753 doi:10.1136/jcp.2008.062547
  • Short report

Rapid blood separation is superior to fluoride for preventing in vitro reductions in measured blood glucose concentration

  1. R Z Shi,
  2. E S Seeley,
  3. R Bowen,
  4. J D Faix
  1. Stanford University, Stanford, California, USA
  1. Run Zhang Shi, Department of Pathology, Stanford University, Stanford, California, USA; rzshi{at}
  • Accepted 10 April 2009


Aims: To determine whether tubes containing sodium fluoride negatively bias blood glucose concentration by directly comparing glucose concentrations in paired blood samples collected in tubes containing lithium heparin (Li-Heparin) and tubes containing sodium fluoride/potassium oxalate (NaF-KOx).

Methods: Paired blood samples from a group of patients (n = 1040) were collected in tubes containing Li-Heparin and tubes containing NaF-KOx at the same time. All Li-Heparin samples were centrifuged soon after collection and were kept cool in transport along with NaF-KOx samples, which were centrifuged at the receiving location after an average transport time of 4 h, but immediately before analysis. Glucose concentrations in the paired samples were determined simultaneously by an automated oxidase method.

Results: The mean glucose concentrations for NaF-KOx samples and Li-Heparin samples were 5.7 mmol/l and 6.1 mmol/l, respectively, with a mean difference of 0.39 mmol/l.

Conclusion: Rapid separation of heparinised blood is superior to fluoride alone for abrogating glycolytic effects on blood glucose measurements in the clinical laboratory.


  • Competing interests: None.