Serum fructosamine determination as an index of glycaemic control: comparison between an automated and manual method, and the effect of serum storage.

The measurement of glycated serum proteins was recently introduced as an alternative index of diabetic control of glycated haemoglobin. Manual and automated serum fructosamine colorimetric assays are available for glycated serum proteins determination. We have assessed two serum fructosamine assays, an automated and a manual method, and compared them with a glycated haemoglobin assay. We also studied the effect of serum storage on serum fructosamine concentrations. Serum fructosamine at four different concentrations measured by automated method gave an inner-assay of a 2% (range 1.29 - 1.56%) and an inter-assay variation of 3% (range 1.63-2.92%). There was a good correlation between the automated and manual methods, with a coefficient of r = 0.944. Serum fructosamine by either method is a sample assay to perform and is relatively inexpensive. With automated analysis, a large number of tests can be performed more rapidly. Comparing serum fructosamine with glycated haemoglobin, coefficients = 0.54 (automated) and r = 0.50 (manual) were obtained. An increase in serum fructosamine by 5-20% occurred when the assay is performed on serum samples stored for more than two weeks. It is recommended therefore that test should be performed soon after blood collection, preferably within one week.