CGM, Not Insulin Pump, 'Is What Makes Difference' in Type 1 Diabetes

Miriam E. Tucker

September 18, 2019

BARCELONA — Use of real-time continuous glucose monitoring (rtCGM) can help improve blood glucose control in people with type 1 diabetes whether they use an insulin pump or multiple daily injections (MDI) of insulin, new research suggests. 

Three-year data from the Comparison of Different Treatment Modalities for Type 1 Diabetes Including Sensor-Augmented Insulin Regimens (COMISAIR) study were presented here at the European Association for the Study of Diabetes (EASD) 2019 Annual Meeting by Jan Šoupal, MD, PhD, Charles University, Prague, Czech Republic.

The results were simultaneously published in Diabetes Care.

At 3 years — the longest duration of any CGM trial — real-time (not flash) CGM was superior to self-monitored blood glucose (SMBG), or fingerstick, testing at least four times daily in reducing HbA1c in patients using both pumps and MDI, with little difference between the two insulin delivery modalities.

Only the rtCGM group had improvements in time-in-range and reduced time below range. Fewer patients using rtCGM experienced severe hypoglycemic episodes. 

"It is not so important how insulin is delivered, but more important is how patients with type 1 diabetes monitor their glucose," Šoupal said during his presentation.

CGM and Whether It Is Real-Time Key to Best Outcomes

Šoupal also said that "CGM and multiple daily injections [of insulin] can be a suitable alternative to treatment with pumps and CGM for some patients," such as those who have achieved good control using that regimen, those who are only willing to accept one device on their bodies, or for reasons of accessibility/affordability.

Patients likely to do better with pump plus CGM regimens include those with the dawn phenomenon (a rise in blood glucose in the early morning) and those who are physically active and can benefit from temporarily lowered basal infusion rates. Patients with hypoglycemic unawareness may be ideal candidates for sensor-augmented pump therapy, he added.

"Individualization of treatment is important. However, according to the results of our trial, in the vast majority of cases, CGM is what makes the difference," Šoupal said.

Asked to comment, Julia Mader, MD, Medical University of Graz, Austria, agreed. "The majority of patients profit from rtCGM whereas the insulin delivery mode is really not that important and should be at the patients' preference. They are equal."

Many of the oIder studies that showed improved glycemic control with insulin pumps were conducted during the time prior to use of insulin analogs, she noted, so that the comparator of twice-daily injections of NPH and Regular insulin versus Regular in the pump is not an accurate reflection of today's modalities. Today, she said, "Multiple daily injection [of insulin] is much better than before."   

Mader also noted that the "real-time" aspect of CGM is important.

Participants in the current study used either the Dexcom G4 or Medtronic Enlite sensors, not the Abbott Libre (ie, "flash" glucose monitoring or FGM).

In her practice in Austria, where many patients use FGM, many don't achieve HbA1c targets with either pump or injection therapy, she noted. That's probably due in part to the alarm feature of rtCGM but not flash monitoring and that flash monitoring is less accurate in the lower ranges of blood glucose levels. 

"Real-time alarms are better than just having the data...I think that's why patients are more cautious," she said.

Mader also cautioned that in some cases the introduction of CGM or flash glucose monitoring might actually lead to an increase in HbA1c if the main initial effect is reducing hypoglycemic events, which should be explained to patients, she advised.

COMISAIR Study Details

The real-world, nonrandomized study compared changes in HbA1c among 94 patients using one of four treatment regimens: insulin pumps with or without rtCGM (15 and 20 patients, respectively) and MDI with or without rtCGM (12 and 18 patients), and all participants also used SMBG.

All patients were adults with type 1 diabetes of at least 2 years' duration and baseline HbA1c 7.0%-10.0% (53-86 mmol/mol). A total of 88 participants completed all 15 study visits at 3-month intervals over 3 years.

At 3 years, the rtCGM + MDI and rtCGM + insulin pump groups had significantly lower HbA1c levels compared with the MDI and pump groups using SMBG, at HbA1c 7.0% (53 mmol/mol), P = .0002, and 6.9% (52 mmol/mol), P < .0001, versus 8.0% (61 mmol/mol), P = .3574, and 7.7% (61 mmol/mol), P = 1.00. There were no significant differences between the two CGM groups or the two fingerstick groups.   

The proportions of patients who achieved HbA1c < 7% at 3 years were 48% with rtCGM + MDI and 43% with rtCGM + pump, compared to just 9% with SMBG + pump and 16% with SMBG + injections. 

Improvements in time-in-range (70-180 mg/dL, 3.9-10.0 mmol/L) were 14.2% with rtCGM + MDI versus SMBG + MDI (P = .0007), 11.1% with CGM + injections versus SMBG + pump (P = .0016), 17.6% with rtCGM + pump versus SMBG + pump (P < .0001), and 14.5% with rtCGM + pump versus SMBG + pump (P < .0001). 

Significant reductions in percentage of time below 70 mg/dL (3.9 mmol/L) were seen in both CGM groups but not the SMBG groups (P = .4847 and P = 1.000), respectively.

A total of seven severe hypoglycemic episodes occurred during the study, of which two were in the SMBG + pump group, three in the SMBG + injections group, and one in the rtCGM + pump group (but the patient was not wearing the CGM at the time). There were three episodes of diabetic ketoacidosis: one in the SMBG + pump group, one in the SMBG + MDI group, and one in the CGM + pump group. All were adjudicated.

COMISAIR was supported by grants from the Agency for Healthcare Research and the Ministry of Health of the Czech Republic. Soupal has reported serving as an advisory board member, consultant, and/or speaker for Novo Nordisk, Eli Lilly, Sanofi, Boehringer-Ingelheim, AstraZeneca, Medtronic, Roche, and Dexcom. Mader has reported being an advisory board member and/or speaker for Becton Dickinson, Boehringer Ingelheim, Eli Lilly, Medtronic, Sanofi, Abbott Diabetes Care, AstraZeneca, Nintamed, Novo Nordisk, Roche Diabetes Care, Sanofi, Servier, and Takeda.

EASD 2019 Annual Meeting. Presented September 19, 2019. Abstract 40.

Diabetes Care. Published online September 17, 2019. Abstract

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