Challenges in diagnosing gestational diabetes after Roux-en-Y gastric bypass: a comparative analysis of OGTT, SMBG, and CGM.

Abstract

Background: Gestational diabetes mellitus (GDM) is a common complication of pregnancy, and the oral glucose tolerance test (OGTT) is the standard diagnostic tool. However, in women after Roux-en-Y gastric bypass (RYGB), OGTT is less reliable and potentially unsafe due to the risk of hypoglycemia.

Objectives: This study compares 3 methods of GDM diagnosis-OGTT, self-monitoring of blood glucose (SMBG), and continuous glucose monitoring (CGM)-in post-RYGB pregnant women to assess and compare their diagnostic performance.

Setting: University Hospital, Switzerland.

Methods: A cohort of 15 pregnant women with a history of RYGB was evaluated between 24 and 28 weeks of gestation. Each participant underwent OGTT, SMBG, and CGM. We assessed the sensitivity, specificity, and concordance of OGTT and SMBG against CGM, which served as the reference test. The incidence of hypoglycemia during OGTT was examined.

Results: Using OGTT, 7 of the 15 participants were diagnosed with GDM, and 8 participants experienced hypoglycemia (glucose levels below 3.0 mmol/L). SMBG diagnosed GDM in 7 participants and CGM identified GDM in 11 participants. There was no significant concordance among OGTT, SMBG, and CGM (φ .26 (-.26 to .67) between OGTT and CGM (P = .57); φ -.07 (-.58 to .44) between OGTT and SMBG (P = 1), φ .26 (-.21 to .67), and between CGM and SMBG (P = .57). OGTT and SMBG demonstrated similar sensitivity and specificity, when compared to CGM (sensitivity of 54.40% and specificity of 75%) even though the patients diagnosed differed between the methods.

Conclusions: In this exploratory study, CGM appears to be a possible approach for diagnosing GDM in post-RYGB patients. SMBG is a commonly available method. OGTT poses risks of severe hypoglycemia. These findings support the need for tailored GDM screening approaches in postbariatric surgery pregnancies and highlight the importance of further research to establish specific guidelines for this population.