Painless and discrete intermittently scanned continuous glucose monitoring in gestational diabetes: as accurate as fingersticks?

Abstract

Gestational diabetes mellitus (GDM) requires close surveillance of blood glucose to prevent perinatal morbidity. Self-monitoring of capillary blood glucose (SMBG) four times a day is routine, but adherence comes with considerable psychosocial and physical burden. Intermittently scanned CGM (isCGM) or flash CGM devices are discrete and could considerably impact the lifestyle of the patient. It is designed to replace SMBG testing in nonpregnant patients. However, data on this technology in pregnancy is scant. The aim of this study was to assess concordance of SMBG with isCGM in GDM. This was an IRB-approved prospective single-arm study evaluating the agreement of isCGM sensor (Freestyle Libre) and SMBG when determining glucose levels fasting and 2 hours postprandial for 14 days. This was documented as percentage of sensor results within Zone A (clinically accurate measurements with no effect on clinical action) or Zone B (values that deviate from reference by >20% but would lead to benign/no treatment) of the Parkes Error Grid. Per International Organization for Standardization (ISO) criteria, agreement was defined as >95% within Zone A or B. Analytical accuracy was evaluated using mean and median absolute relative difference (ARD) and mean and median absolute difference (AD). There were 1604 pairs of SMBG/isCGM observations for 41 patients. Mean glucose values were 102.0 (SD 20.5) mg/dL and 89.4 (SD 20.1) mg/dL for SMBG and isCGM, respectively (Fig 1). The mean and median AD were 15.9 and 13.0 mg/dL, respectively. Mean and median ARD were 15.9% and 12.5%, respectively. Zones A and B contained 76.9% and 22.9% of values in the Parkes Error Grid, for a total of 99.8% (Fig 2). Our data suggests that glucose values with the isCGM trended lower, with greater mean and median ARD than prior studies. SMBG and isCGM demonstrated concordance on the Parkes Error Grid. However, given the strict glycemic control required during pregnancy, physicians should be aware of these differences in their management, possible clinical implications and safety.View Large Image Figure ViewerDownload Hi-res image Download (PPT)