Phoenix Lab recently introduced our two new state-of-the-art Siemens Atellica chemistry analyzers. We have done extensive testing, validation and correlations with our previous AU chemistry analyzers to ensure quality results. Although we are using the same reagent with the Atellica, the use of this new analyzer has resulted in a significant change in our fructosamine reference interval. The new reference interval is closer to published reference intervals.
New Fructosamine Reference Interval beginning July 10, 2019
Cat: 204-376 umol/L — Dog: 209-339 umol/L
Old Fructosamine Reference Intervals June 8, 2018 until July 9, 2019
Cat: 176-324 umol/L —- Dog: 180-292 umol/L
When comparing fructosamine concentrations on the same patient between one run on the previous analyzer and one on the Atellica, remember to compare the results relative to their reference ranges and not to each other. For example, a fructosamine concentration for a cat run on the Atellica is 370 umol/L. Previously, the value run last month on the old analyzer was 370 umol/L. The value has not changed but the previous value was high and the current value within the normal range.
Fructosamine is the product of an irreversible reaction between glucose and the amino groups of plasma proteins. It is generally assumed to reflect the mean blood glucose concentration of the preceding approximately two weeks, although this has not been well established in dogs and cats and may actually be shorter.
Diagnosis of Diabetes: Fructosamine may be helpful in distinguishing stress-induced hyperglycemia from diabetes. Fructosamine is not affected by short-term increases in blood sugar; therefore, fructosamine is usually normal in stress hyperglycemia.
Insulin Regulation of Diabetes: Fructosamine is one piece of assessing diabetic control. It remains important that the pet’s clinical signs, attitude, owner assessment of the pet’s diabetic control, pet’s weight, presence/absence of glucosuria, and a glucose curve be assessed prior to evaluating a fructosamine concentration. Fructosamine concentration may be most helpful when the value is low. A low fructosamine value would suggest persistent hypoglycemia and indicate a need to confirm suspected insulin over dosage with a blood glucose curve. A normal to high fructosamine concentration is not specific and can occur with hypoglycemia (with a Somogyi effect), normoglycemia and hyperglycemia.
Fructosamine is potentially helpful when trending over time.
We recommend measuring blood glucose concurrently with fructosamine. Preferably this would be done at the nadir when the lowest blood sugar is expected. This one time value, whether low, normal, or high may be very helpful in the interpretation of the fructosamine. Fructosamine concentration should never be used as the sole indicator of diabetic control.
Note also that protein concentrations, marked hyperlipidemia, marked hemolysis and thyroid status can significantly affect the fructosamine concentration. A recent study showed that uncontrolled feline hyperthyroidism alone could decrease the fructosamine by up to 200 umol/L (Vet Sci 2017, 4, 17) which may result in a misdiagnosis of stress hyperglycemia in a hyperthyroid cat that may in fact be diabetic. Another study (Vet Res Commun 2002, 26, 531) showed that uncontrolled hypothyroidism in nondiabetic dogs can falsely increase fructosamine but in those patients, fructosamine was < 440 umol/L. Following therapy, fructosamine values returned to the reference range in 8 to 24 weeks, lagging behind resolution of hypothyroidism with supplementation.
Fructosamine in Diabetes
The following guidelines may be used to get a sense of diabetic control in conjunction with clinical assessments:
Published Fructosamine Ranges from Feldman and Nelson (Canine and Feline Endocrinology, 4th edition, 2015): Guidelines Only as reference ranges vary slightly between laboratories.
Rule-out prolonged hypoglycemia if fructosamine < 350 umol/L or if there is any history of weakness or other clinical signs of hypoglycemia.
If you have any questions regarding interpretation of fructosamine results, please contact the lab for a consultation at (425) 355-5252 (toll free at 1-800-347-0043).