Colorimetric determination of non-enzymatically glycated albumin

A colorimetric method was developed for the determination of nonenzymatically glycated albumin and adapted to a Flexigem centrifugal analyzer. Albumin was separated from serum or plasma using Sepharose-blue dextran affinity chromatography. The stable ketoamine linkage in glycated albumin reduced a tetrazolium salt to its colored formazan. Glycated human serum albumin was used as the standard and optimum conditions for the assay were established. Recovery of glycated albumin was quantitative. The coefficients of variation for within-run and day-to-day precision were 4.6% and 8.5%, respectively. The labile aldimine fraction, lipemia, icterus, hemolysis and type of anticoagulant used did not affect the results. The non-diabetic reference interval for this method was 7.9-11.6% glycated albumin, and normal and diabetic populations can be clearly discriminated (p less than 0.005). Values obtained with this method correlated well with a thiobarbituric acid assay (r = 0.974) but less so with those for glycated hemoglobin (r = 0.35).