Fructosamine

Fructosamine is a general term that applies to any glycated protein formed by the nonenzymatic reaction of glucose with the amino groups of proteins. The nonenzymatic glycation of proteins in vivo is proportional to the prevailing glucose concentration during the lifetime of the proteins. Albumin is the most abundant serum protein and accounts for 80% of fructosamine. Some assays claim to measure glycated total protein while others measure glycated albumin. 

Albumin has a circulating half life of approximately 17 days, compared to 120 days for HbA1c. Fructosamine is considered to be an intermediate indicator of diabetic control because it is not as immediate as blood glucose, but not as longstanding as HbA1c. In general, fructosamine levels reflect glycemic control over the previous 2 to 3 weeks. 

Fructosamine is most useful when measurement of HbA1c is unreliable due to a hemoglobinopathy or hemolysis. Fructosamine values are not accurate in individuals with serum albumin levels below 3 g/dL or when serum albumin turnover is accelerated. Examples include cirrhosis, nephrotic syndrome, thyroid disease and paraproteinemia. 

Fructosamine is measured by a colorimetric assay. Reference range is 200–285 umol/L. People with poorly controlled diabetes typically have a mean fructosamine value of 396 umol/L, while some have values as high as 565 umol/L. 

Specimen requirement is a red top tube of blood. 

References

Kirkman SM and Sachs DB, Glycated Albumin: Added Value or Redundancy in Diabetes Care? Clin Chem 2022; 68:379-81.