Quantification of nonenzymically glycated albumin and total serum protein by affinity chromatography.

We have evaluated an affinity-chromatographic procedure for determination of glycated albumin (GA) and glycated total serum protein (GSP). Recovery of these analytes was inversely related to free glucose concentration, thus necessitating removal of free glucose. For this we used molecular-exclusion chromatography on G-25 Sephadex, or dialysis, the latter procedure resulting in significantly (p less than 0.05) lower concentrations of GSP and GA. Total protein concentration and percent glycation are also inversely related, and so protein concentrations must be standardized before the assay. Within- and between-run CVs for both GSP and GA were less than 6.5 and 18%, respectively, the determination of GA being generally the more precise of the two. Labile glycated fractions, lipemia, icterus, hemolysis, and type of anticoagulant did not affect the results, but assay temperature did. Diabetic subjects showed substantially higher concentrations of GA and GSP than did normal subjects. Because of the life span of these analytes in circulation, their measurement may provide a short-term index of glycemic control.