Accuracy of a portable glucose meter and of a Continuous Glucose Monitoring device used at home by patients with type 1 diabetes

Abstract

BackgroundPatients with diabetes are recommended to self-monitor their blood glucose levels also at home. Accuracy of a hand-held glucometer and a Continuous Glucose Monitoring (CGM) device were comparatively evaluated. MethodsVenous blood samples (for reference laboratory determinations; n=428) were collected from 18 type 1 patients (35–65years old), immediately followed by capillary measurement (Bayer ContourLink meter) and CGM readings (Medtronic Paradigm). ResultsLaboratory values did not differ statistically from ContourLink and CGM readings, mean difference (±SD) being −0.05±1.06mmol/L and 0.10±1.84mmol/L glucose, respectively. A bias ((value−reference)/reference×100) ≥15% was observed in 27.7% and 54.9% of cases, respectively. Notably, below 3.9mmol/L glucose (hypoglycemic threshold), an absolute error>0.8mmol/L was found in 78.9% and 94.1% of cases. The absolute errors of the CGM device were inversely related to the rate of glucose change (r=0.598, p<0.001). ConclusionsA very large error was observed at the extreme glycemic values, which may lead to erroneous therapy. Consequently, performance of future portable glucometers should be focused in particular under hypo- and hyper-glycemia. Moreover, integrated CGM devices should not disregard the effect of the rate of blood glucose change on the sensor readings.