Calibrating Blood Glucose Monitoring Systems

Background: Blood glucose monitoring systems should give results close to "real blood glucose" values for reliable measurement, so manufacturers of such systems are required to implement an effective reference method for glucose measurement. Methods: The highest-order method of measuring blood glucose, isotope dilution gas chromatography/mass spectrometry (ID/GC/MS), combines gas chromatography (GC) and mass spectroscopy, and is calibrated and controlled using certified primary reference materials from the National Institute of Standards and Technology in the US. Time-consuming sample preparation keeps ID/GC/MS from routine use, so the hexokinase method is used instead with direct alignment to the reference method using a three-stage calibration hierarchy to establish traceability between the hexokinase method and ID/GC/MS. Results: The ID/GC/MS method currently provides the most accurate results the uncertainty value of the whole analytical procedure accumulates to +/- 1.7% (95% confidence interval). More than 95% of all control measurements lie within the 1.7% range. Conclusions: Reliable glucose measurement requires an unbroken traceability chain from reference material to measurement results obtained by blood glucose monitoring systems; laboratory methods that do not allow glucose measurement traceability should be abandoned.