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Continuous Glucose Monitoring Systems

Continuous glucose monitoring (CGM) systems are used to measure interstitial glucose levels at regular intervals, usually once every one-to-five minutes, thereby showing trends in glucose measurements that cannot be obtained with traditional blood glucose monitoring. A conventional CGM system consists of a glucose sensor, a transmitter, and a monitor. The sensor is implanted just under the skin and attaches to a non-implanted transmitter that sends information to a pager-sized wireless monitor. In addition to stand-alone CGM systems, several insulin pump systems have built-in CGM.

CGM may be short-term or long-term. With short-term CGM, the sensors and monitor are attached in the clinic and worn by the patient for 3 to 5 days. Glucose values are not visible to the patient, but are downloaded and interpreted by a physician after completion of the monitoring period. This is also referred to as professional or retrospective CGM. Examples of U.S. Food and Drug Administration (FDA) approved professional (short-term) CGM systems are the iPro®2 Professional CGM and the G6 Professional CGM.

Long-term CGM utilizes the same technology as short-term CGM, but glucose values are immediately available to the patient and the device may be used for longer periods. A monitor displays glucose values and issues an alarm if values are above or below prespecified measures. Patients can also download information to a computer and print reports documenting their glucose patterns. These systems are also referred to as personal or real-time CGM. Examples of FDA-approved personal (long-term or real-time) CGM systems include the following (list is not all inclusive): Dexcom G6® and G7® CGM System and the FreeStyle Libre Glucose Monitoring Systems.

Closed-Loop Continuous Glucose Monitoring and Insulin Pump Systems (Artificial Pancreas Device Systems)

Closed-loop systems, also called an artificial pancreas device system (APDS), consist of CGM, an insulin pump, and a computerized algorithm that communicates with both. The goal of the APDS is to monitor glucose levels and adjust insulin levels without direct patient input. Examples of FDA-approved APDS devices include the MiniMed™ closed-loop system that integrates an insulin pump with CGM, and includes a low glucose suspend (LGS) feature. The LGS feature temporarily suspends insulin delivery when interstitial glucose levels fall below a preset threshold. When the glucose value reaches this threshold, an alarm sounds. If patients respond to the alarm, they can choose to continue or cancel the insulin suspend feature. If patients fail to respond to the alarm, the pump automatically suspends insulin delivery for 2 hours, and then resumes action.  The MiniMed 670G System is a hybrid closed-loop CGM and insulin pump system with a semi-automatic insulin adjustment feature. The MiniMed 670G System is approved for patients with type 1 diabetes who are at least 7 years old. The MiniMed 770G System is similar to the MiniMed 670G and offers blue-tooth-enabled technology. It is intended for use in patients 2 years of age and up requiring insulin as well as for the continuous monitoring and trending of glucose levels.

Glucose Monitoring Devices Integrated with Remote Monitoring Capability

Several FDA-approved devices integrated with remote monitoring via computer application or Bluetooth® technology are available. These include the Guardian® Connect System for continuous or periodic monitoring of glucose levels in the interstitial fluid under the skin in patients (14 to 75 years of age) with diabetes mellitus. The system provides real-time glucose values and trends through a Guardian Connect app installed on a compatible consumer electronic mobile device. It allows users to detect trends and track patterns in glucose concentrations. The Guardian® Connect app alerts if a Guardian® Sensor 3 glucose level reaches, falls below, rises above, or is predicted to surpass set values. The Guardian Sensor glucose values are not intended to be used directly for making therapy adjustments, but rather to provide an indication of when a finger stick may be required. All therapy adjustments should be based on measurements obtained using a home glucose monitor and not on values provided by the Guardian Sensor 3.The Guardian Connect system is comprised of the following devices: Guardian Connect app, Guardian Sensor 3, and the Guardian Connect transmitter. The Guardian Connect app is available over-the-counter (OTC) but requires the Guardian Sensor 3 and Guardian Connect transmitter to function. The sensor and transmitter are available only by prescription.

The Dexcom G6® and G7® Integrated Continuous Glucose Monitoring (iCGM) devices can be used as part of an integrated system with other compatible medical devices and electronic interfaces, which may include automated insulin dosing systems, insulin pumps, blood glucose meters or other electronic devices used for diabetes management. The Dexcom G6® and G7®  are patch devices applied to the skin of the abdomen. They contain small sensors that continuously measures the amount of glucose in body fluid, transmitting real-time glucose readings every 5 minutes to a compatible display device such as a mobile medical app on a cell phone. In addition, the Dexcom G6® and G7®  are factory calibrated and do not require users to calibrate the sensor with fingerstick blood glucose measurements. An updated sensor probe minimizes interference with acetaminophen.

Glucose Monitoring Devices with Implantable Sensors

FDA approved the Eversense® CGM system for use in patients 18 years of age and older with diabetes. This is the first FDA-approved CGM system to include a fully implantable sensor to detect glucose, which can be worn for up to 90 days. The system consists of 3 components: an implantable fluorescence-based cylindrical glucose sensor measuring 3 mm × 16 mm, a wearable smart transmitter, and a handheld device running a mobile medical application. The transmitter is worn over the implanted sensor for continuous readout of glucose data, but can be removed and replaced without the need for sensor replacement. The system works in tandem with a mobile application that allows for the real-time display of interstitial glucose readings. The sensor is inserted in the upper arm under local anesthesia via a 5-8 mm incision in a procedure that takes around 5 minutes to complete, and can be performed in an office setting. The sensor removal procedure is similar to the insertion procedure. The system requires the patient or caregiver to perform twice daily calibration with a fingerstick self-monitoring blood glucose (SMBG) meter

I.    Professional (Short-Term) Continuous Glucose Monitoring (CGM) Systems

• Use of a professional (short-term) CGM system for 3 to 5 days may be considered MEDICALLY NECESSARY AND APPROPRIATE for patients with diabetes who meet ONE of the following criteria:
  • Diabetes is poorly controlled, as evidenced by unexplained hypoglycemic episodes, hypoglycemic unawareness, suspected postprandial hyperglycemia, or recurrent diabetic ketoacidosis; OR
  • Prior to insulin pump initiation to determine basal insulin levels.
• All other uses of a professional (short-term) CGM system are considered EXPERIMENTAL/INVESTIGATIVE due to the lack of evidence demonstrating an impact on improved health outcomes.

II.   Personal (Long-term or Real-Time) Continuous Glucose Monitoring (CGM) Systems

• Use of a personal (long-term or real-time) CGM system may be considered MEDICALLY NECESSARY AND APPROPRIATE for patients with diabetes who meet ONE of the following criteria: 
  • Type 1 diabetes; OR 
  • Type 2 diabetes AND ONE of the following: 
    • Insulin dependent; OR 
    • High risk for hypoglycemia (e.g., history of severe hypoglycemia requiring assistance to manage) and/or impaired awareness of hypoglycemia; 
  • OR 
  • During pregnancy.
• All other uses of a personal (long-term or real-time) CGM system are considered EXPERIMENTAL/INVESTIGATIVE due to the lack of evidence demonstrating an impact on improved health outcomes.

III.  Closed-Loop Continuous Glucose Monitoring (CGM) and Insulin Pump Systems (Artificial Pancreas Device Systems)

• Use of an FDA-approved closed-loop CGM and insulin pump system (artificial pancreas device system) with a low-glucose suspend feature may be considered MEDICALLY NECESSARY AND APPROPRIATE for patients with diabetes who meet ALL of the following criteria:
  • Type 1 or insulin-dependent type 2 diabetes; AND
  • Meets FDA-approved age requirements for the specific system being used; AND
  • Insulin injections are required 3 or more times per day or an insulin pump is used for maintenance of glucose control.
• All other uses of a closed-loop CGM and insulin pump system (artificial pancreas device system) are considered EXPERIMENTAL/INVESTIGATIVE due to the lack of evidence demonstrating an impact on improved health outcomes.

IV.   Implantable Interstitial Glucose Sensors

• Use of an FDA-approved implantable interstitial glucose sensor is considered EXPERIMENTAL/INVESTIGATIVE due to the lack of evidence demonstrating an impact on improved health outcomes.