The relationship between capillary and venous glucose concentration during pregnancy

Previous attempts to construct capillary equivalents of venous glucose values for prognostic purposes have failed. We examined the relationship between capillary and venous glucose concentration during pregnancy in 258 women who had samples taken at four different time intervals in relation to two different standardized meals. Capillary glucose concentration was determined with the Chemstrips bG and an Accu-Chek reflectance colorimeter and venous plasma glucose concentration was measured by the hexose kinase technique on an AutoAnalyzer. The capillary: venous relationship was constant over time for a given meal but the magnitude of the difference was affected by time. The capillary: venous relationship differed significantly between the two standard meals. The findings indicate that meal size and sampling time must be controlled for when one is attempting to construct capillary equivalents for venous derived norms. The failure of previous studies to control for these variables may explain their inability to construct useful capillary equivalents for venous glucose values. Our findings also indicate that attainment of venous norms with capillary specimens represent, in reality, tighter control.