fructosamine

Fructosamine refers to a group of glycated serum proteins formed when reducing sugars, primarily glucose, react nonenzymatically with amino groups on proteins such as albumin. In clinical use, the term describes the mixture of these glycated proteins that is measured to assess glycemic control over a shorter time frame than other markers.

Formation and measurement: The glycation process begins with the formation of a Schiff base between a reducing sugar and an amino group on a protein, which rearranges to a more stable Amadori product. In routine laboratories, the fructosamine concentration reflects average blood glucose levels over roughly two to three weeks, corresponding to the turnover of serum proteins. The common laboratory method is a colorimetric fructosamine assay, often based on the nitroblue tetrazolium reaction, though alternative assays exist. Results are typically reported in micromoles per liter and can vary by methodology.

Clinical use: Fructosamine testing is used to monitor short-term glycemic control, especially when HbA1c measurements are unreliable or not available. It is helpful during situations with altered red blood cell turnover or hemoglobin variants, such as certain anemias, recent transfusions, pregnancy, or rapid changes in therapy. It can provide a more immediate sense of glucose management than HbA1c.

Limitations and interpretation: Fructosamine levels depend on the amount and turnover of circulating proteins, particularly albumin. Conditions that affect protein levels or turnover—such as hypoalbuminemia, liver disease, nephrotic syndrome, or malnutrition—can influence results. Additionally, assay variability and interference from lipids or other factors can affect accuracy. Therefore, fructosamine is best interpreted alongside clinical context and other laboratory data, and it is not a stand-alone replacement for HbA1c.