Plasma protein glycation as measured by fructosamine assay.

The fructosamine test for assessing control of glucose in blood has been extensively evaluated, but some questions remain regarding its validity. From the analytical and clinical evaluation we present here, we conclude that: the test is sensitive to variations in the composition of the sample protein; the fructosamine reaction is almost completely unaffected by labile fractions; the concentrations of fructosamine correlate well with the degree of glycation of total serum proteins, especially with glycated albumins and glycated immunoglobulins, as determined by affinity chromatography; the correlation with glycated hemoglobin (Hb A1c), measured as the stable fraction, is very poor, in diabetics treated with insulin (r = 0.373), or with oral hypoglycemic agents (r = 0.390); and (e) fructosamine and Hb A1c are, in fact, expressions of different periods of metabolic control and therefore have different clinical meanings.