Radioimmunoassay of glycosylated albumin with monoclonal antibody to glucitol-lysine.

An immunoassay specific for glycosylated albumin was developed by the use of beads coated with antibody to human serum albumin (beads) and 125I-labelled monoclonal antibody to reduced bovine glucosylated low density lipoprotein. One bead was capable of binding 100 ng of serum albumin which had been treated with sodium borohydride (NaBH4) to reduce the Schiff base in the protein. The monoclonal antibody reaction with glucitol-lysine epitopes on the reduced glucosylated proteins and amino acids studied, including human serum albumin (HSA), bovine serum albumin and hippuryl-L-lysine. The detection limit of this assay was 100 pmol/mg HSA, which was sensitive enough for clinical use. The mean serum reduced glycosylated albumin concentration measured by this new method was significantly higher in diabetic patients (2.63 +/- 0.35 nmol/mg HSA, n = 32) than in healthy subjects (0.53 +/- 0.05 nmol/mg HSA, n = 38). The serum reduced glycosylated albumin concentration correlated with both hemoglobin A1c (r = 0.69, p less than 0.005) and the fasting blood glucose level (r = 0.51, p less than 0.005) in diabetic patients.