Fructosamine

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

These two proteins are markers of mean blood glucose concentration, with their concentration being proportional to the blood glucose concentration. The concentration of these proteins is not affected by stress; they are ideal for monitoring diabetic animals, particularily cats.

Fructosamine

The bonding of glucose to proteins produces fructosamines. A single fructosamine measurement indicates the average glucose concentration over the previous 2-3 weeks, based on the half-life of the plasma proteins.

The majority of diabetic animals will not always have optimal control of blood glucose thus fructosamine concentrations are unlikely to lie entirely within the reference range. Single fructosamine measurements should be interpreted in the light of clinical signs of diabetes, body weight and blood glucose concentration. In general, the closer the fructosamine concentration is to the reference range for healthy dogs and cats, the better the glycemic control.

Fructosamine reference ranges

Fructosamine reference ranges for dogs
DogsFructosamine values
(micromol/l)
Normal non-diabetic dog225-365
Newly diagnosed diabetic dog320-850
Treated diabetic dogs:
Excellent control350-400
Good control400-450
Fair control450-500
Poor control>500

(Reference: Feldman EC, Nelson RW (2004) Canine diabetes mellitus. In Canine and Feline Endocrinology and Reproduction. 3rd edition. Saunders, St Louis, USA p. 510)

Fructosamine reference ranges for cats
CatsFructosamine values
(micromol/l)
Normal non-diabetic cat190-365
Newly diagnosed diabetic cat350-730
Treated diabetic cats:
Excellent control350-400
Good control400-450
Fair control450-500
Poor control>500

(Reference: Feldman EC, Nelson RW (2004) Feline diabetes mellitus. In Canine and Feline Endocrinology and Reproduction. 3rd edition. Saunders, St Louis, USA p. 563)

Advantages and limitations of fructosamine values
Advantages of measuring fructosamineLimitations of fructosamine measurements
Distinguishes hyperglycaemic, non-diabetic animals from diabetics with chronic hyperglycaemiaUnable to detect short-term or transient abnormalities in the blood glucose concentration, e.g. hypoglycaemia.
Does not appear to be influenced by transient (stress) hyperglycaemiaHyperthyroid cats with diabetes mellitus may have decreased fructosamine concentrations, despite having normal serum protein concentrations due to an increase in the protein turnover rate (decreased protein half-life) due to increased thyroid hormone concentrations.
Useful in confirming diagnosis in catsIncrease in hyperproteinaemia (e.g. dehydration).
Useful in evaluating longer-term control and owner compliance with insulin treatmentDogs with hypoalbuminaemia also have a decreased fructosamine concentration (false negative).

Fructosamine in Diagnosis and Monitoring of Diabetes in dogs and cats

In practice fructosamine is often used as an aid to the diagnosis and monitoring of diabetic cats.