Fructosamine

Fructosamine is a compound that can be considered the result of a reaction between fructose and ammonia or an amine (with a molecule of water being released). A fructosamine is also formed when carbonyl group of glucose reacts with an amino group of a protein, as the double bond to oxygen moves from the end carbon atom to the next carbon atom and water is released. Fructosamines formed from blood proteins such as serum albumin are known as Glycated Serum Protein (GSP) or Glycated Albumin, and are used to identify the plasma glucose concentration over time and so assess diabetic control over an intermediate period of time.^[1]

Indications

Glucose control is usually assessed in diabetes with the Glycosylated hemoglobin measurement that indicates average glucose levels over the preceding 12 weeks, as reflected by the permanent glycosylation of a small fraction of the hemoglobin molecules in their blood. However, this is not appropriate where there has been a recent change in diet or treatment within 6 weeks, or if there are abnormalities of red blood cell aging or mix of hemoglobin subtypes (predominantly HbA in normal adults). Hence people with recent blood loss or hemolytic anemia, or hemoglobinopathy such as sickle-cell disease, are not suitable for some glycosylated hemoglobin methods that do not account for higher-turnover hemoglobin. Fructosamine is used in these circumstances, as it also reflects an average of blood glucose levels, but over a shorter period of 2 to 3 weeks. Fructosamine is also of use in conditions, such as pregnancy, in which hormonal changes cause greater short-term fluctuation in glucose concentrations.

Interpretation of results

There is no standard reference range available for this test. The reference values depends upon the factors of patient age, gender, sample population, and test method. Hence each laboratory reports will include their specific reference range for the test. An increase in fructosamine in lab testing results usually means an increase in glucose in the blood.

Approximately each change of 3.3 mmol (60 mg/dl) in average blood sugar levels will give rise to changes of 2% HbA1c and 75 µmol fructosamine values.^[2] However this over emphasises the upper limit of many laboratories' reference ranges of 285mmol/l as equivalent to HbA1c 7.5% rather than 6.5%. A comparative study,^[3] which has been used in official advice for Quality and Outcomes Framework guidance in the UK^[4] and summaried by the United States' National Quality Measures Clearinghouse:^[5] gives the following formula and resulting values:

Hence:

See also

• Diabetes mellitus

Footnotes

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