fructosamin

Fructosamine, often written as fructosamin, is a collective term for glycated serum proteins formed when reducing sugars such as glucose react non-enzymatically with amino groups on proteins. The reaction produces a stable ketoamine linkage, known as an Amadori product, with serum albumin being the principal carrier of fructosamine in the bloodstream, along with other proteins such as transferrin.

Formation occurs through the initial reaction of a carbonyl group of a reducing sugar with a free amino group on a protein, creating a Schiff base that rearranges to a more stable fructosamine (ketoamine) adduct. These glycated proteins accumulate over the protein’s lifespan and reflect average circulating glucose during that period.

Clinically, fructosamine measurement provides information about average blood glucose over roughly the preceding two to three weeks, shorter than the two to three months reflected by HbA1c. It is used to monitor glycemic control in diabetes and can be particularly useful when HbA1c results may be unreliable due to conditions that affect red blood cell turnover, such as certain hemoglobinopathies or recent transfusions.

Laboratory testing for fructosamine is typically a colorimetric spectrophotometric assay, often based on the reduction of a colorimetric indicator by the fructosamine moiety. Results are reported as fructosamine concentration or as an equivalent glucose concentration, depending on the assay. Interpretation should consider factors that alter serum protein levels or turnover, such as liver or kidney disease, nephrotic syndrome, malnutrition, or protein-losing states, which can influence fructosamine values independently of glycemia.