Plasma 1,5-anhydroglucitol concentrations are influenced by variations in the renal threshold for glucose

Aims Measurement of serum 1,5-anhydroglucitol (1,5AG) concentrations has be en proposed as an alternative to HbA(1c) as both a marker of diabetic glyca emic control and as a screening rest for diabetes. The sugar competes with glucose for renal tubular reabsorption, so hyperglycaemia leads to reduced serum 1,5AG concentrations through increased urinary loss. This study has s ought to establish whether plasma 1,5AG can be influenced by nut only hyper glycaemia, but by variations in renal threshold fur glucose. Methods Thirty-eight pregnant women (median age 30 years, range 20-43) foun d to be normoglycaemic after a 75-g carbohydrate load had plasma 1,5AG and urine glucose measured. Results Using multivariate analysis, the presence and degree of detectable glycosuria at 2h post glucose load was strongly predictive of a low plasma 1,5AG concentration (P=0.0012) independently of lasting plasma glucose (P=0 .96), 2h glucose (P=0.029), subject age (P=0.97) and gestation (P=0.36). Th us, when matched fur plasma glucose areas under the glucose load curve, 16 glycosuric subjects had significantly lower 1,5AG concentrations compared t o 16 nonglycosuric ones (median 1,SAG 46 mu mol/l (IQR 30-56) vs. 72 mu mol /l (IQR 55-79, P=0.017). Conclusions People with the same glucose tolerance may demonstrate variable plasma 1,5AG concentrations depending on their renal threshold for glucose . This inherent characteristic is likely to limit the usefulness of the tes t when monitoring or screening for diabetes.