Continuous glucose monitoring could show potential in identifying gestational diabetes and capturing clinically relevant glucose patterns, but current evidence may not support replacing the oral glucose tolerance test as the diagnostic standard, according to a review.
In the narrative review, investigators evaluated studies focused on continuous glucose monitoring (CGM) for diagnosing gestational diabetes mellitus (GDM), including observational studies and randomized controlled trials involving pregnant patients across multiple populations. The investigators assessed CGM-derived metrics such as time of CGM wear and activity; mean glucose; glucose management indicator; glycemic variability; and time in range, above range, or below range compared with oral glucose tolerance test (OGTT) results and pregnancy outcomes. The investigators hoped to determine whether CGM could support or replace OGTT-based diagnosis as well as to examine associations with adverse maternal and neonatal outcomes and the need for pharmacotherapy.
Across the studies, CGM metrics differentiated patients who later developed GDM from those who didn't. Higher mean glucose levels, greater glucose variability, and more time above target glucose ranges were observed as early as 13 to 14 weeks’ gestation and persisted into the second trimester in patients subsequently diagnosed with GDM. Some measures demonstrated moderate predictive performance, with area under the receiver operating curve values approaching 0.8.
CGM-derived glucose patterns were also associated with clinically relevant outcomes. Patients with greater time above target glucose levels had higher likelihood of adverse neonatal outcomes, including large-for-gestational-age infants, shoulder dystocia, neonatal injury, respiratory distress, and neonatal hypoglycemia. In addition, CGM-detected glucose excursions showed stronger correlations with birth weight centiles compared with standard OGTT testing in some studies.
Randomized trials evaluating CGM for the management of GDM showed mixed findings. Some studies reported lower rates of large-for-gestational-age births and neonatal intensive care unit admissions when CGM was used alongside pharmacotherapy, whereas others found no statistically significant difference in composite maternal or neonatal outcomes compared with self-monitored blood glucose.
Despite the findings, the investigators emphasized that CGM hasn't been validated as a diagnostic replacement for OGTT. Differences between CGM and plasma glucose measurements as well as the absence of standardized diagnostic thresholds may limit clinical adoption. The investigators noted that any future diagnostic criteria would likely need to be device specific.
The evidence base was limited by its reliance on observational data for diagnostic performance, heterogeneity in study design and CGM devices, and the lack of outcome-based diagnostic thresholds. Many randomized trials weren't powered to detect differences in clinical outcomes, and adherence to CGM use varied across the studies.
The investigators concluded that CGM may complement existing screening strategies but will require further validation in randomized controlled trials before it can be used diagnostically.
“Current evidence is insufficient to support CGM as a standalone diagnostic test for GDM,” wrote lead study author M. Crowley, of Galway University Hospital in Ireland, and colleagues.
The study authors reported no competing interests and no external funding.
Source: BMC Medicine