COMPARISON OF MICRO-ENZYMATIC AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC METHODS FOR THE ASSAY OF SERUM 1,5-ANHYDROGLUCITOL

Serum 1,5-anhydro-D-glucitol (AG) has been proposed as a marker of glycaemic control in diabetic patients. Two methods have been developed which could be applied to routine clinical monitoring of serum AG. We have compared the assay characteristics of an adapted enzyme assay, based on the enzyme pyranose oxidase, with a high-performance anion-exchange chromatographic method using pulsed amperometric detection (HPAEC-PAD). Linearity and minimum detectable concentrations were practically identical (to at least 400 mu mol/l and 4 mu mol/l AG, respectively), though intra- and inter-assay precision was better with the HPAEC PAD system at a clinically relevant concentration of 40 mu mol/l AG (9.8% vs. 11.8% and 9.2% vs. 13.0%, respectively). The recovery of added AG to serum samples was lower with the micro-enzyme assay than the HPAEC-PAD assay (74 +/- 15% vs. 102 +/- 8%). Despite good agreement by linear regression (r=0.974, P<0.005), the assay methods did not demonstrate satisfactory agreement when using a difference plot (limits of agreement -16.1 to 18.7 pmol/l). We conclude that although both assay methods are applicable to routine analyses, the HPAEC-PAD is more precise and is more specific for AG than the enzyme based assay.