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A Randomized Trial Comparing Use of Continuous Glucose Monitoring With and Without Routine Blood Glucose Monitoring in Adults with Type 1 Diabetes (REPLACE)


Continuous glucose monitoring (CGM) offers the opportunity to improve glycemic control, including a reduction in hypoglycemia. However, current FDA CGM device labeling is labeled as an adjunct to self-monitoring of blood glucose rather than a replacement. Further, the Centers for Medicare and Medicaid Services (CMS) does not provide coverage for CGM as CGM devices do not meet the Medicare definition of durable medical equipment and do not fall under any other Medicare benefit category. A study comparing CGM used solely as an adjunctive device, as per the FDA labeling, versus CGM used largely in lieu of Blood Glucose Monitoring (BGM) measurements would provide valuable data. If indeed insulin dosing decisions are proven to be safe and effective using CGM alone (without BGM confirmation) compared to CGM with BGM confirmations, this study would also pave the way for a new standard diabetes management protocol and therapy that would not require eight BGM measurements (i.e. finger sticks) a day and ease the burden of managing type 1 diabetes. The primary objective of the study is to determine whether the routine use of CGM without BGM confirmation is as safe and effective as CGM used as an adjunct to BGM. The study design is a 6-month parallel group multi-center randomized noninferiority clinical trial. The study population includes adults >18 years old with T1D for at least 1 year who (1) are using an insulin pump, (2) have HbA1c level <9%, (3) have had no severe hypoglycemia in the last 12 months requiring assistance of another individual for treatment and no events resulting in seizure of loss of consciousness in the past 3 years, and (4) have no significant hypoglycemia unawareness. Successful run-in includes compliance with use of CGM >21 days during the prior 28 days and an average of >4 BGM measurements must have been made on at least 90% of days. Subjects with CGM values <60 mg/dl for more than 10.0% will not be eligible for randomization. Subjects will be randomly assigned with 2:1 probability to the CGM Only and CGM+BGM groups, respectively. The primary outcome will be the time in range of 70 to 180 mg/dl, measured with CGM over the full 6 months of the study. Analyses will follow the intent-to-treat principle with all participants analyzed in the group to which they were randomized. The primary analysis will include all participants. The relationship between the time in range and the treatment group will be examined through a least squares regression model adjusting for baseline time in range, CGM user at time of enrollment, and possibly clinical center. If the number of participants per clinical center is too small to include center as a fixed effect (<10 participants/center) then clinical center will be included as a random effect instead. Previous data suggest that the time in range is typically approximately normally distributed so a transformation should not be necessary. However, this will be explored and a transformation or nonparametric analyses will be used instead if the data are highly skewed. A one-sided 95% confidence interval for the difference in treatment groups (CGM+BGM group minus CGM Only group) will be computed.



Inclusion and Exclusion Criteria

  • To be eligible, all participants must meet the following inclusion criteria:
  • Clinical diagnosis of type 1 diabetes (based on investigator's judgment)
  • Age >=18 years
  • T1D duration >=1
  • HbA1c <=9.0% (a local laboratory or DCA2000 or comparable point of care device will be used to assess eligibility)
  • Use of an insulin pump for insulin delivery for at least 3 months, with no plans to discontinue pump use during the next 8 months
  • Participant is able to manage his/her diabetes with respect to insulin administration and glucose monitoring, as assessed by the investigator during the screening visit
  • Participant understands the study protocol and agrees to comply with it, including willingness to use the study CGM and BGM
  • No expectation that participant will be moving out of the area of the clinical center during the time period of the study, unless the move will be to an area served by another study center

  • Individuals who meet any of the following criteria are not eligible for the study:
  • Severe hypoglycemia in the last 12 months in which the assistance of another individual was needed or seizure/loss of consciousness in the past 3 years
  • Significant hypoglycemia unawareness based on the Clarke Hypoglycemia Unawareness Survey defined as at least one of the following being present: - Survey score >2 - Survey Q1 is answered as 'I no longer have symptoms when my blood sugar is low' - Survey Q7 response indicates that symptoms of hypoglycemia are not felt until glucose level is <50 mg/dl - Survey Q8 response is never or rarely to the question 'to what extent can you tell by your symptoms that your blood sugar is low'
  • More than one DKA event in the past year
  • History of seizures other than due to hypoglycemia
  • Current use of a threshold suspend pump feature (note: participant is eligible if a pump with this feature was being used but the threshold suspend was not active)
  • Myocardial infarction or stroke in past 6 months
  • Estimated Glomerular Filtration Rate (GFR) <30 obtained within the prior 12 months as part of usual care or kidney transplant
  • Most recent thyroid function test results abnormal, obtained as part of usual care within the prior 2 years
  • The presence of a significant medical or psychiatric disorder or use of a medication that in the judgment of the investigator will affect the wearing of the sensors, the completion of any aspect of the protocol, or increase risk
  • Cognitive difficulties that, in the judgment of the investigator, could impair the individual's ability to follow the protocol or increase risk
  • Initiation of a non-insulin drug for glucose control during the past 3 months, planned initiation during the next 8 months, or discontinuation of a non-insulin drug for glucose control during the past 3 months (note: individuals using a non-insulin medication for glucose control for 3 or more months are eligible provided there is no expectation that the medication will be discontinued during the time period of study participation)
  • Use of a systemic beta blocker drug
  • Regular use of oral corticosteroids
  • Anticipated need to use acetaminophen during the time course of the study
  • Inpatient psychiatric treatment in the past 6 months
  • Currently pregnant or lactating or plan to attempt getting pregnant during the time period of the study


Please contact Valerie Ruelas to learn more about where you can participate in this trial. Please use the contact form on the right side.

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