Measuring glycaemia

The treatment of diabetes mellitus is dependent on many factors. Since high glucose is a hallmark of the disease and a main factor in determining the risk for complications and adverse outcomes, glucose monitoring is a cornerstone of any management plan. Particularly when implementing complex treatment protocols such as multiple daily insulin therapy, one must know the level of glucose and how it varies throughout the day, weeks and longer term. Measurement of glycaemia encompasses both measurement of glucose itself and of biological substrates that reflect the longer-term alterations in glucose such as HbA1c (glycosylated hemoglobin), fructosamine and 1,2-anhydroglucitol. The methodology, benefits and limitations of each of these are discussed in this section.

Glucose measurement

'The doctor' by J.A. van Staveren. Inspecting and tasting urine for sweetness was one of the first diagnostic procedures.
'The doctor' by J.A. van Staveren. Inspecting and tasting urine for sweetness was one of the first diagnostic procedures.
Various forms of glucose monitoring have evolved through history.
Already in ancient India, the response of ants to glucose-rich and thus sweet urine was used as diagnostic tool. With the development of chemistry as a science, urine glucose measurement and later blood glucose measurement as part of conventional laboratory studies became common practice. This was followed by the development of home blood glucose monitoring devices (HBGM) which were initially extremely bulky and expensive. These became more compact, more sophisticated and more accurate. Several of the meters now are capable of communicating with insulin pump systems. Newer meter systems are being developed to integrate with smart phones and provide additional information and assist with glucose control. HBGMs measure whole blood and remain the standard in measuring glycemia on a personal level. Recently continuous glucose monitoring devices or CGMs have become available but are still have issues with accuracy in the hyper and hypoglycemic ranges. CGMs measure interstitial fluid and have differences when compared to home monitoring meters. Improvement in these devices will advance the treatment of both Type 1 and Type 2 diabetes mellitus. CGM will be essential in the development of closed loop systems.

Measures of long-term glycaemia

Fructosamine

Fructosamine is the reaction product of glucose attaching to the aminogroups of proteins. It reflects the fasting and post-prandial glucose variability over a 6 week period. It's limitations are the short duration of measurement. It is useful in individuals with gestational diabetes. It does not substitute for HbA1C in most cases.

HbA1c and glycated Hemoglobin

Hemoglobin A1C (Glycated Hemoglobin) is a glycosylated subfraction of hemoglobin. It is a measure of both fasting and post-prandial glucose control over a 6-12 week period. It was initally proposed for use in patients with diabetes mellitus by Koenig et al in 1976. [1] It can be reported in percentage or mmol/mol. It estimates the average glucose. It has also been considered useful in the diagnosis of diabetes but this is still controversial. Recently, the FDA has approved an A1C test for the diagnosis of diabetes.

1,5-Anhydroglucitol (1,5-G) or Glycomark

Glycomark or 1,5 Anhydroglucitol, measures only post-prandial glucose over a limited time period. In combination with Hemaglobin A1C measurements, it can assist in determining the areas of improvment needed, whether fasting or postprandial. [2] The use of Glycomark is increasing and has provided a useful tool in discussions with patients.

References

  1. ^ Koenig RJ, Peterson CM, Jones RL, Saudek C, Lehrman M, Cerami A (1976). "Correlation of glucose regulation and hemoglobin AIc in diabetes mellitus". N. Engl. J. Med. 295 (8): 417–20.

  2. ^ Dungan J, Buse J et al. (1,5-Anhydroglucitol and Postprandial Hyperglycemia as Measured by Continuous Glucose Monitoring System in Moderately Controlled Patients with Diabetes. Diabetes Care. 2006; 29:6:1214-1219)

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