Several classes of protein may undergo non-enzymetic addition of glucose derived product. Hemoglobin was the first protein shown to be modified. Subsequent studies have demonstrated a similar effect of glucose on lens crystalline, collagen, erythrocyte membrane proteins, albumin and other serum proteins.

Measurement of these non-enzymatic glycosylated serum proteins (GSP) showed that the levels were approximately two to three times higher in diabetic than non-diabetic subjects. In diabetic patients the mean + SD of GSP was 0.693 + 0.257 (SD) nmol HMF per mg protein compared with 0.355 + 0.108 (SD) in controls
(P< 0.001). in diabetic patients levels appear to reflect glycemia in the preceding several days and correlate with other parameters of diabetes such as FBS. In this study non-enzymaticaly  glycosylated serum protein measured by a colorimetric assay in 96 diabetic and 37 control subjects and relationship of GSP to FBS was shown.