Limitations of blood glucose monitoring in type 2 diabetes

Pat Phillips



Self-monitoring of blood glucose levels by people with diabetes is useful to guide decisions by the individual and healthcare professionals. However, it is important to understand and allow for the intrinsic and remediable limitations of blood glucose monitoring and know how to assess and correct causes of excess inaccuracy and variability.

Key Points

  • Blood glucose monitoring (BGM) is useful to guide decisions by patients and healthcare professionals but its intrinsic and remediable limitations should be understood and allowances made for them.
  • Problems with the BGM system affecting results include interference by ambient conditions, the haematocrit, medications, postprandial samples and reliability of blood glucose strips.
  • Problems associated with the BGM user affecting results include errors in coding, strip storage, recording results and sample contamination.
  • BGM variability is assessed by the coefficient of variation; components include measurement and biological variabilities.
  • BGM results vary in their accuracy and variability but US and international standards are that 95% of BGM test results lie within 5% or 15%, respectively, of the true BGL value.
  • The reliability of BGM results can be assessed by performing BGM immediately before and after a blood sample is taken for laboratory measurement of BGL: the lower the difference between the average of the two BGM results and the laboratory value, the higher the accuracy; and the lower the difference between the BGM results, the lower the variability.

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