Glycosylated Haemoglobin

Fructosamine and glycosylated haemoglobin (GHb) are two glycated proteins commonly used for monitoring diabetics.

The two proteins are markers of mean blood glucose, with their levels being proportional to the blood glucose concentration. The concentration of these proteins is not affected by stress; they are ideal for monitoring diabetic animals. In practice they are particularly useful for the diagnosis and monitoring of diabetic cats.

Glycosylated haemoglobin is produced by the non-enzymatic, irreversible binding of glucose to haemoglobin in erythrocytes. The glycosylation of haemoglobin is a gradual process and is not affected by acute or transient hyperglycaemia.

Glycosylated (glycated) haemoglobin concentration can be used as a screening test for diabetes mellitus, as well as for the monitoring of glycemic control in treated diabetic animals, based on red blood cell lifespan.

Advantages of GHb measurements

• Unaffected by stress related or post-prandial hyperglycaemia.
• Useful in long term monitoring of diabetic animals over the previous 2-3 months.

Limitations of GHb measurements

• Test not widely available for dogs and cats
• Not the most responsive test due to the relatively long erythrocyte lifespan life span (approximately 110 days in dogs and <68 days in cats).
• Less effective for short-term monitoring than fructosamine because hyperglycaemia must be present for at least 3 weeks before increased HbA1c values are detectable.
• Affected by haemoglobin concentrations: may be increased or decreased due to polycythaemia or anaemia, respectively.