medwireNews: Advanced hybrid closed loop (AHCL) therapy with the MiniMed 780G system does not improve overall time in glycemic range versus standard insulin therapy in pregnant women with already tight glycemic control, study findings indicate.
However, women using the MiniMed 780G (Medtronic, Northridge, California, USA) spent more time in overnight target range, less time below range, and reported greater treatment satisfaction than those using standard insulin therapy, report Katrien Benhalima (KU Leuven, Belgium) and co-authors in The Lancet Diabetes & Endocrinology.
They say their data suggest that the AHCL device “can be safely used in pregnancy and provides some additional benefits compared with standard insulin therapy; however, it will be important to refine the algorithm to better align with pregnancy requirements.”
The CRISTAL study included 95 pregnant women aged 18–45 years with type 1 diabetes who were randomly assigned to receive AHCL therapy with the MiniMed 780G (n=46) or standard insulin therapy (n=49) beginning at a median of 10.1 weeks’ gestation. At baseline, the mean glycated hemoglobin (HbA1c) level was 6.5% (7.8 mmol/L) and 95.8% of participants were using insulin pumps.
Overall, the mean proportion of time spent in the pregnancy-specific target glucose range (3.5–7.8 mmol/L; 63.1–140.6 mg/dL) during pregnancy was similar between the AHCL and standard therapy groups, at 66.5% versus 63.2%. Measurements were taken using continuous glucose monitoring throughout weeks 14–17, 20–23, 26–29, and 33–36 of pregnancy and averaged across the four time periods.
Overnight time spent in the target range was significantly higher in the AHCL arm than in the standard insulin therapy arm, at 75.1% versus 67.2%, corresponding to an additional 24 minutes per night, on average.
Women using the AHCL system also spent a significant 19 fewer minutes per day with target glucose levels below 3.5 mmol/L (63.1 mg/dL) than those using standard insulin therapy (2.5 vs 4.1% of time spent below range) and a significant 7 fewer minutes per night (1.9 vs 4.2% of time).
Other significant differences between the two arms included overnight time above target range and glycemic variability, both of which favored AHCL therapy.
There was no difference between the two groups in other glycemic control markers such as mean HbA1c, mean glucose, or overall time spent above target range, and the researchers note that a mean target glucose range greater than 70% was only reached between 33–36 weeks of pregnancy.
Nonetheless, women using AHCL therapy reported significantly higher treatment satisfaction on the Diabetes Treatment Satisfaction Questionnaire and were significantly more aware of hypoglycemia based on the Gold score than those using standard therapy.
There were no unanticipated adverse events and the “findings suggest that the MiniMed 780G is safe for use in pregnancy,” Benhalima et al remark.
They also point out that the “study was not powered for pregnancy outcomes,” but these were generally similar between the groups, with no differences in preterm birth rates, cesarean sections, or neonatal complications.
In an accompanying comment, Helen Murphy (University of East Anglia, Norwich, UK) and Eleanor Scott (University of Leeds, UK) describe the findings as “disappointing, particularly in the context of experienced insulin pump users with excellent baseline glycaemia.”
They say the lack of significant improvement in overall time in range is “in stark contrast to the beneficial effects of using the Medtronic 780G system outside pregnancy, and to the findings of the AiDAPT trial, which reported a clinically relevant 10.5% higher time spent in the pregnancy-specific target glucose range among Cam APS FX closed-loop users from 16 weeks’ gestation until delivery.”
Murphy and Scott point out that all CRISTAL participants “had similar glycaemic benefits, regardless of their baseline HbA1c.” They therefore suggest that the differences in glycemic outcomes between the two trials “are more likely to be attributed to differences between the closed-loop systems than differences in user characteristics.”
In agreement with Benhalima and co-investigators, the commentators say that “it will be important to refine the Medtronic 780G algorithm to better align with pregnancy requirements before it can be recommended for use during pregnancy.”
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Lancet Diabetes Endocrinol 2024; doi:10.1016/S2213-8587(24)00089-5
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