Differences in venous, capillary and interstitial glucose concentrations in individuals without diabetes after glucose load

Abstract

Abstract Objectives Differences between capillary and venous glucose concentrations have been reported in the past. In continuous glucose monitoring (CGM) system performance studies, comparator measurements are often performed in venous samples, despite CGM systems typically aiming at providing capillary-like values. In this study, differences between venous, capillary and interstitial glucose concentrations, measured with a laboratory analyzer, a self-monitoring of blood glucose (SMBG) system and an intermittent-scanning CGM system were investigated in subjects without diabetes after glucose load. Methods During the study, an oral glucose tolerance test (oGTT) was performed with 41 participants who had no known history of diabetes (mean age 25.5 ± 9.7 years). Venous blood samples for measurement with a laboratory analyzer were collected before drinking the standardized 75 g glucose solution and after 60 and 120 min. In parallel, capillary blood was obtained for measurement with a laboratory analyzer and an SMBG system, and interstitial glucose values were measured with an intermittent-scanning CGM system. Results Glucose concentrations in the fasting state were slightly different for the three different compartments whereas considerable differences (some median differences exceeding 30 %) in glucose concentration were observed 60 and 120 min after the start of the oGTT. Conclusions Marked differences with a high inter-individual variability between venous, capillary, and interstitial fluid glucose concentrations were found especially after glucose load. These differences can affect perceived CGM accuracy in performance studies depending on the specific comparator method used, and they are potentially relevant in clinical practice, like diabetes diagnosis.