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Am J Perinatol 2023; 40(11): 1149-1157
DOI: 10.1055/a-2053-7650
SMFM Fellowship Series Article

Comparison of an Intermittently Scanned (Flash) Continuous Glucose Monitoring System to Standard Self-Monitoring of Capillary Blood Glucose in Gestational Diabetes Mellitus

Farrah N. Hussain 
1   Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Mount Sinai West, Icahn School of Medicine at Mount Sinai, New York, New York
,
Samantha Raymond
2   Department of Population Health Science and Policy, Icahn School of Medicine at Mount Sinai, New York, New York
,
Kristina M. Feldman 
1   Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Mount Sinai West, Icahn School of Medicine at Mount Sinai, New York, New York
,
Sophia Scarpelli-Shchur
1   Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Mount Sinai West, Icahn School of Medicine at Mount Sinai, New York, New York
,
Tirtza S. Strauss
1   Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Mount Sinai West, Icahn School of Medicine at Mount Sinai, New York, New York
,
Zainab Al-Ibraheemi
1   Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Mount Sinai West, Icahn School of Medicine at Mount Sinai, New York, New York
,
Lois Brustman
1   Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Mount Sinai West, Icahn School of Medicine at Mount Sinai, New York, New York
› Author Affiliations Funding None.
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Abstract

Objective Gestational diabetes mellitus (GDM) requires close surveillance of blood glucose to prevent perinatal morbidity. Self-monitoring of capillary blood glucose (BGM) comes with considerable psychosocial burden. Intermittently scanned continuous glucose monitor (isCGM) devices are discreet and could considerably impact the lifestyle of the patient. They are designed to replace BGM testing in nonpregnant patients. Data on this technology in pregnancy are scant. The aim of this study was to assess concordance of BGM with isCGM in GDM.

Study Design Institutional review board approved prospective single-arm study evaluating agreement of isCGM (Freestyle Libre 14-day system) compared with BGM when determining glucose levels fasting and 2-hour postprandial for 14 days. This was documented as percentage of 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 (developed for nonpregnant patients with diabetes). Per International Organization for Standardization criteria, agreement was defined as >95% within Zone A or B. Analytical agreement was evaluated using mean and median absolute relative difference (ARD), mean and median absolute difference (AD).

Results There were 1,604 pairs of BGM/isCGM observations for 41 patients. Mean glucose values were 102.0 (standard deviation [SD] = 20.5) and 89.4 (SD = 20.1) mg/dL for BGM and isCGM, respectively. 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, respectively, in the Parkes Error Grid, for a total of 99.8%.

Conclusion BGM and isCGM demonstrate clinical agreement. However, glucose values with isCGM trended lower, with greater mean and median ARD than prior studies. Given the strict glycemic control required during pregnancy, physicians should be aware of these differences and their possible clinical implications.

Key Points

  • Gestational diabetes mellitus requires close surveillance of blood glucose.

  • isCGM is painless and discreet; however, values trend lower than capilary blood glucose.

  • Physicians should be aware of these differences and possible clinical implications.

Keywords

gestational diabetes - continuous glucose monitoring - glycemic control - freestyle libre

Note

Abstract was presented at the Society for Maternal-Fetal Medicine 42nd Annual Pregnancy Meeting, February 2022.




Publication History

Received: 14 September 2022

Accepted: 24 February 2023

Accepted Manuscript online:
14 March 2023

Article published online:
10 April 2023

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