Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (937 page)

FRUCTOSAMINE, SERUM

   Definition

   Fructosamine describes serum proteins that have been glycated (i.e., derivatives of nonenzymatic reaction product of a sugar [glucose] with serum protein [albumin]). It reflects the mean glucose concentration in blood over recent period (2–3 weeks), whereas glycated Hb (HbA
_1c
) is indicative of blood glucose over intermediate to long term (4–8 weeks).

   
Normal range
(nondiabetic individuals): 170–285 μmol/L.

   Use

   To assess short-term glycemic control in diabetic patients.

   When glycated Hb cannot be used due to interferences (e.g., abnormal Hb), which invalidate HbA
_1c
.

   It should be compared with previous values in the same patient rather than reference range.

   Interpretation

Increased In

   Hyperglycemia in patients with poorly controlled DM

   Limitations

   Because the assay is nonspecific, color may be generated by compounds other than glycated proteins. Interferences are seen from ascorbic acid (vitamin C) and elevated bilirubin values. However, the second-generation assays have been shown to be highly specific for glycated proteins.

   Fasting blood glucose and HbA
_1c
are the usual and preferred means of monitoring glycemic control.

   Changes in fructosamine values correlate with significant changes in serum protein concentrations (e.g., liver disease, acute systemic illness). Abnormal values also occur during abnormal protein turnover (e.g., thyroid disease), even though patients are normoglycemic. It may be obviated by using fructose: albumin ratio.