Continuous Glucose Monitoring After Gastric Bypass to Evaluate the Glucose Variability After a Low-Carbohydrate Diet and to Determine Hypoglycemia
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Roux-en-Y gastric bypass (RYGB) alters glucose metabolism and can cause postprandial hypoglycemia. Continuous glucose monitoring (CGM) has been proposed as an evaluation tool in hypoglycemic RYGB individuals. The objective of this study is to investigate the use of CGM in clinical decision-making including diagnosing hypoglycemia and evaluating treatment effects. Furthermore, we aim to assess its accuracy in RYGB-operated individuals.
Thirteen RYGB individuals with symptomatic hypoglycemia and 13 asymptomatic RYGB individuals underwent CGM for 5 days. During this period, a mixed-meal test with concomitant plasma glucose (PG) measurements was performed. Furthermore, the RYGB individuals followed a low-carbohydrate diet (LCD) for 1 day and maintained their ordinary diet (OD) for the rest of the period.
LCD reduced the CGM-determined glycemic variability of the mean interstitial fluid glucose (IFG) significantly compared to OD (p < 0.0001). Receiver operating characteristic analysis confirmed that low blood glucose index (e.g., the frequency and amplitude of hypoglycemic events) is the most reliable parameter related to the development of symptomatic hypoglycemia, with a sensitivity of 0.91 (confidence interval [CI] 0.59; 1.00) and a specificity of 0.77 (CI 0.46; 0.95). However, CGM, measuring the IFG in the subcutaneous adipose tissue, overestimated the minimum glucose levels by 1.1 ± 0.9 mmol/l compared with PG.
CGM was a good method for demonstrating increased glycemic variability among RYGB individuals and for displaying dietary effects on reducing this glycemic variability, including hypoglycemic events. In RYGB individuals, CGM-measured IFG overestimated the real glucose value by about 1 mmol/l in the hypoglycemic range. This should be taken into consideration if CGM is used to diagnose hypoglycemia after RYGB.
KeywordsRoux-en-Y gastric bypass Continuous glucose monitoring Hypoglycemia measurement Low-carbohydrate diet Glucose variability Method comparison
We thank Lenette Pedersen and Pia Hornbek for their very skillful technical assistance and Nurse Dorthe Møller for helping with the patients during the study. We thank Bayer HealthCare for supporting the delivery of Contour Next meters and test strips for the measurement of glucose.
This study has primarily been supported by the Central Denmark Region, but the A.P. Møller Maersk Foundation and the Novo Nordisk Foundation have also supported this study.
Compliance with Ethical Standards
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The protocol was approved by the Regional Ethics Committee and registered in Clinicaltrial.gov (1-16-02-138-13).
Conflict of Interest
The authors declare that they have no conflicts of interests.
Written informed consent was obtained from all participants included in the study. Additional informed consent was obtained from all individual participants for whom identifying information is included in this article.
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