Implantable Continuous Glucose Monitors (I-CGM)

Title XVIII of the Social Security Act, §1862(a)(1)(A) excludes expenses incurred for items or services which are not reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member.

Title XVIII of the Social Security Act, §1862(a)(7) excludes routine physical examinations.

CMS Internet-Only Manual, Pub. 100-08, Medicare Program Integrity Manual, Chapter 13, §13.5.4 Reasonable and Necessary Provision in an LCD

Compliance with the provisions in this LCD may be monitored and addressed through post payment data analysis and subsequent medical review audits.

Covered Indications

Continuous glucose monitors (CGMs) are class III medical devices that require premarket approval by the United States Food and Drug Administration (FDA). In order to be considered reasonable and necessary, the FDA approved indication must include use as a therapeutic CGM.¹ The FDA recently approved expanding the indications of an implantable CGM (I-CGM) product to replace fingerstick blood glucose measurements for diabetes treatment decisions.

Therapeutic I-CGMs are considered reasonable and necessary by Medicare when all of the following coverage criteria (1-4) are met:

1. The beneficiary has diabetes mellitus (DM) (Refer to the ICD-10 code list in the LCD-related Billing and Coding Article for applicable diagnoses); and,
2. The beneficiary’s treating practitioner has concluded that the beneficiary (or beneficiary’s caregiver) has sufficient training using the I-CGM prescribed as evidenced by providing a prescription; and,
3. The I-CGM is prescribed in accordance with its FDA indications for use; and,
4. The beneficiary for whom an I-CGM is being prescribed, to improve glycemic control, meets at least 1 of the criteria below:
   1. The beneficiary is insulin-treated; or,
   2. The beneficiary has a history of problematic hypoglycemia with documentation of at least 1 of the following:
      1. Recurrent (more than one) level 2 hypoglycemic events (glucose < 54 mg/dL (3.0 mmol/L)) that persist despite multiple (more than one) attempts to adjust medication(s) and/or modify the diabetes treatment plan; or,
      2. A history of one level 3 hypoglycemic event (glucose < 54 mg/dL (3.0 mmol/L)) characterized by altered mental and/or physical state requiring third-party assistance for treatment of hypoglycemia

CGM Continued Coverage

Every 6 months following the initial prescription of the CGM, the treating practitioner conducts an in-person or Medicare-approved telehealth visit with the beneficiary to document adherence to their CGM regimen and diabetes treatment plan.

Limitations

I-CGM devices will not be considered reasonable and necessary for short-term (72 hours to 1 week) diagnostic use.

Exception: For those beneficiaries who have previously met the coverage criteria for a non-implantable therapeutic CGM through the Medicare durable medical equipment (DME) benefit and subsequently choose to switch to the implantable device, they may do so with a provider order. However, all other coverage criteria above must be fulfilled in order for Medicare payment.

Background

DM is a chronic metabolic disease involving an underproduction or resistance to insulin, resulting in elevated blood glucose levels. The 2 most common types of diabetes are type 1 (T1DM) and type 2 (T2DM).² T1DM comprises approximately 5-10% of diabetes cases and describes an etiology in which an autoimmune response damages the insulin-producing beta cells of the pancreas, resulting in insufficient insulin production. Conversely, T2DM is characterized by insulin resistance.^2,3 In T2DM, an individual’s insulin production fails to offset the deficit that is created by the resistance.² T2DM constitutes an estimated 90%-95% of diabetes cases.³

Approximately 11.3% of Americans have diagnosed diabetes, and an additional 3.4% of Americans are estimated to have undiagnosed diabetes. The prevalence of diabetes is known to increase with age. In Medicare aged populations in the United States (U.S.) (≥ 65 years of age), 22.4% of the population has diagnosed diabetes, with an additional 4.7% estimated to have undiagnosed diabetes.⁴ Economic evaluations have estimated that diabetes annually accounts for $237 billion in direct U.S. medical expenditure, and an additional $90 billion in lost productivity.⁵

Acute complications of diabetes include hypoglycemia, hyperglycemia, diabetic coma, and nonketotic hyperosmolar coma. Chronic hyperglycemia, resulting from poorly controlled diabetes, may result in serious and life-threatening damage, including dysfunction and failure of the eyes, kidneys, nervous system and cardiovascular system. The complications of DM are far less common and less severe in people who have well-controlled blood sugar levels.²

To prevent and/or delay the development of both short- and long-term complications of diabetes, the American Diabetes Association (ADA) recommends person-centered care aimed at timely treatment decisions following evidence-based guidelines. Person-centered care goals include minimizing the progression of hyperglycemia with more intensive approaches for individuals at higher risk which include those with higher glucose levels (e.g., fasting blood glucose 110-125 mg/dL, 2 hour post-challenge glucose 173-199 mg/dL, A1C > 6.0%).⁶

Diabetes treatment relies on diet, exercise, lifestyle modifications, and in many, medications in order to keep their blood sugar under a stable and controlled level. Close glucose monitoring either multiple times a day or continuously may be warranted in those diabetics that are having difficulty maintaining that level.^2,7

CGM devices measure glucose via interstitial fluid instead of blood. CGM systems traditionally rely on a multi-part system that often involves: 1.) a sensor that is inserted into subcutaneous tissue; 2.) a receiver/mobile application consisting of a display and interface; 3.) a transmitter component that is attached to the sensor and worn externally.^7,8 The sensors for these subcutaneous CGM systems need to be removed and replaced every 6- to 14-days depending upon the system.⁷

Despite the number of benefits that subcutaneous CGM offers in the DM management paradigm, some CGM studies have reported relatively high attrition rates that patients attributed to discomfort, contact dermatitis, issues changing the sensors, and physical interference with activities of daily living.⁹ The rationale for I-CGM seeks to circumvent these negative patient experiences. Unlike with subcutaneous CGM, I-CGM involves a sensor that is surgically implanted for longer spans of time between replacement, allowing for skin barrier closure, and less frequent manipulation.

The primary aim of this summary of evidence is to determine if I-CGM performs with equivalent clinical validity, efficacy, safety, and patient perceived benefit when compared with subcutaneous CGM devices. The secondary aim of this summary of evidence is to evaluate the expected magnitude of benefit across the aforementioned outcomes resulting from the inclusion of I-CGM into the diabetes management paradigm.

At the time of this review, the Eversense E3^® is the only device that has received clearance for use by the FDA. However, it is this Medicare Administrative Contractor’s expectation that additional devices are in the development and/or FDA approval process and soon may be publicly available. Hence, this LCD is written to reflect coverage criteria and accompanying evidentiary review and analysis on I-CGM devices in an agnostic manner without the endorsement of any specific product.

FDA Approvals

Eversense^® Continuous Glucose Monitoring System: https://www.accessdata.fda.gov/cdrh_docs/pdf16/P160048A.pdf

Literature Analysis

Clinical Validity

The accuracy of CGM devices is most commonly assessed by evaluating mean absolute relative difference (MARD). The MARD value represents the average percent difference between glucose readings that are concurrently obtained at multiple timepoints via an index test (I-CGM in this instance) and via an established reference standard test. MARD is then reported as a percentage, with lower values signifying a higher degree of test accuracy.¹⁰ For reference, 1 narrative review reported that the majority of CGM systems achieve an average MARD of between 9% to 14%, and that a MARD of < 10% had been discussed as a threshold for a CGM system that is accurate enough to inform insulin dosage decisions.¹¹ Thirteen of the studies (14 publications) identified by the literature search evaluated the accuracy of I-CGM with MARD.^12-25

Four of these 13 studies performed comparative analyses analyzing the accuracy of I-CGM compared with subcutaneous CGM systems.^13,14,18,20

Fokkert and colleagues conducted a multi-test diagnostic cohort study among 23 athletes with T1DM. All 23 participants utilized an Eversense^® device, Free Style Libre (FSL) Flash Glucose Monitoring (FGM) system (subcutaneous CGM), and FSL Precision NeoPro strips (diagnostic standard). During normal activity among this sample of patients, Eversense^® performed with a MARD of 13% ± 6%, and the FSL FGM system had a MARD of 12% ± 5%; differences in these MARD values were not statistically quantified.¹⁸

One study conducted a 3-way MARD analysis, comparing the accuracy of Eversense^®, the FSL Pro system (subcutaneous CGM), and the Dexcom^® G5 system (DG5) in a head-to-head fashion, with the StatStrip Xpress^® meter serving as the diagnostic standard. In this trial, 23 adults with T1DM utilized all 4 glucose monitoring devices over a 6-week timespan. Over the course of this trial, the authors reported that the MARD of Eversense^® was 14.8% ± 14.8%; FSL Pro performed with a MARD of 16.3% ± 15.4%, and the MARD of Libre Pro was 18.0% ± 17.9%. Jafri, et al. then performed a pairwise comparison between these 3 MARD values, and determined that in this study, DG5 was significantly more accurate (P=0.004) than FSL Pro, and Eversense^® was significantly more accurate than both DG5 (P=0.008) and FSL Pro (P<0.000).²⁰

Boscari and colleagues performed 2 separate trials comparing the MARD of Eversense^® with that of DG5. In the first trial, 11 adults with T1DM and HbA1c > 10% at baseline were enrolled, and Yellow Spring Instruments (YSI) 2300 STAT Plus was used as the reference standard. Over the 1-week follow-up, the MARD of I-CGM (11.4% [interquartile range (IQR): 5.04% to 18.54%]) was statistically significantly less accurate (signed-rank test P<0.05) compared with that of DG5 (7.91% [IQR: 4.14% to 14.30%]).¹³ The second trial was designed as a crossover randomized controlled trial (RCT) study, in which 16 adults with T1DM and HbA1c < 10% underwent 12 weeks of DG5 and 12 weeks of Eversense^®, with self-monitoring of blood glucose (SMBG) serving as the reference test. Among this sample of 16 participants, the MARD of Eversense^® (12.27% ± 11.55%) was significantly more accurate (P<0.001) when compared with the MARD of DG5 (13.14% ± 14.76%).¹⁴

Nine single-test diagnostic accuracy studies were also identified; these publications assessed the MARD of I-CGM compared against a diagnostic reference standard (YSI 2300 STAT Plus, SMBG, or venous blood laboratory measurements). Among these 9 studies, the average MARD of I-CGM ranged between 8.8% to 12.3%.^{15-17,19,21-25}

Clinical Efficacy

Glycated hemoglobin (HbA1c) is a key measure used to evaluate diabetes risk and morbidity.² Although the ADA recognizes that individual HbA1c normal ranges may vary, they recognize 7% as the standard threshold which most adult diabetics try to stay below.²⁶ None of the 16 studies included in the literature review performed a comparative analysis of HbA1c change between I-CGM and subcutaneous CGM. However, 6 noncomparative studies meeting inclusion did assess HbA1c among patients using Eversense^®, including 3 that performed a pretest-posttest analysis. Among those 3 before-and-after trials, all 3 determined that mean HbA1c levels statistically significantly decreased between baseline (mean: 7.4% - 7.6%) and final study follow-up (mean: 6.9% - 7.19%).^16,21,27 No statistical analyses were performed in the other 3 studies evaluating HbA1c, but all 3 noted a trend of HbA1c reduction following management with I-CGM.^14,19,28

Time in range (TIR) is an often-utilized surrogate outcome, used to evaluate the efficacy of diabetes management. TIR measures the percentage of time that CGM readings fall within the target blood glucose range (commonly defined as between 70 – 180 mg/dL).^10,29 One study was identified that directly compared TIR between patients using I-CGM systems and those utilizing subcutaneous CGM systems.¹⁴ Boscari, et al. (2022) conducted a crossover RCT trial in which patients underwent 12 weeks of management with Eversense^® I-CGM and 12 weeks of management with the DG5 system. Results of this study showed that on average, 71.14% ± 12.29% of the I-CGM group readings were in the target range, which was statistically significantly favored (P<0.028) when compared with the 66.99% ± 11.8% mean TIR exhibited by the DG5 group. Four additional studies also evaluated TIR, but only among patients managing DM with I-CGM.^23,24,27,28 One of these 4 studies performed a pretest-posttest statistical analysis among 100 adults with T1DM. Irace, et al. found that diabetes management with Eversense^® was associated with a significant improvement of TIR compared with baseline.²⁷ For 3 of the 4 noncomparative trials evaluating mean TIR during management with Eversense^®, the mean TIR was between 62.3% - 69% ^23,24,27; the fourth study had multiple different cohorts based upon patient characteristics and could not be pooled.²⁸

Patient Reported Outcome Metrics (PROMs)

Boscari, et al. (2022) was the only publication that comparatively analyzed PROMs between I-CGM and subcutaneous CGM.¹⁴ In this crossover trial, all 16 patients underwent 12 weeks of management with the Eversense^® system and 12 weeks with the DG5. Patient quality of life (QOL) was measured with the validated 17-item Diabetes Distress Scale (DDS), which asks respondents to evaluate each item with a 6-point Likert Scale ranging from 1 (no problem) to 6 (serious problem). Eversense^® was statistically significantly favored compared with DG5 for the total DDS score (I-CGM, 2.1 ± 1.1; DG5, 2.6 ± 1.4; P=0.009) as well as for the emotional burden domain score (I-CGM, 2.1 ± 1.0; DG5, 2.7 ± 1.4; P=0.01), regimen-related distress domain score (I-CGM, 2.1 ± 1.1; DG5, 2.7 ± 1.3; P=0.007), and the interpersonal distress score (I-CGM, 2.0 ± 1.1; DG5, 2.6 ± 1.2; P=0.003). Only the physician-related distress domain score was not significantly different (P=0.12) between DG5 and Eversense^® groups. Patient satisfaction with CGM devices was measured with the Diabetes Treatment Satisfaction Questionnaire (DTSQ), which is an 8-item survey that patients are to score between 0 (not satisfied) and 6 (extremely satisfied). The average total DTSQ score provided by respondents using Eversense^® (31.2 ± 4.3) was not significantly different (P=0.96) when compared with the mean DTSQ respondent score for the DG5 system (31.3 ± 3.9).¹⁴

Two noncomparative studies (3 publications) evaluated patient perceived change in QOL following diabetes management with I-CGM.^12,21,28 Among the 3 publications, QOL was assessed with the 36-Item Short Form Health Survey (SF-36), 28-Item DDS, and the Audit of Diabetes Dependent Quality of Life (ADDQoL) questionnaire. Only 1 of these 2 trials performed a before-and-after statistical analysis, and the authors concluded that no significant change in QOL was observed over time.²⁸ Three noncomparative studies evaluated patient satisfaction with varying PROMs.^12,16,28 One trial found that 84% of respondents would choose to be re-inserted with Eversense^® for implantation cycle if given the opportunity.¹² Christiansen and colleagues examined patient satisfaction with the validated CGM Satisfaction Scale Questionnaire, which asks patients to rate items on a Likert Scale ranging from 1 (lowest satisfaction/largest hassle) through 5 (most satisfaction/least hassle).¹⁶ This study found that among the 35 respondents, the mean overall satisfaction score with I-CGM was 3.9 ± 0.6. Among the respondents, only 20% of I-CGM users indicated that they would be unwilling to use I-CGM again after the study concluded. A third study found that the median DTSQ score over 180 days changed between a median of 0-2 points, which was not statistically quantified.²⁸

Safety

None of the 16 primary studies meeting inclusion for the evidentiary review performed a comparative safety analysis between I-CGM and subcutaneous CGM.

However, 10 noncomparative studies assessed the safety profile of I-CGM. Six of the 10 studies considered the incidence of serious adverse events (SAEs), with all 6 reporting that no SAEs occurred.^{15,17,19,21,27,30} Additionally, 2 studies stated that no adverse events (AEs) occurred at all during study follow-up.^13,14 For the remaining 8 studies assessing, the heterogeneity of how AEs were grouped together and reported precluded the pooling of event rates across studies. Generally, events were infrequent, and mostly consisted of transient skin irritation at the patch site, site infection, pain, and difficulty removing the sensor during first attempt.^{15,16,19,21,23,27,28,30}

Professional Society Recommendations

While the American Diabetes Association (ADA), American Association of Clinical Endocrinology (AACE), Diabetes Canada Clinical Practice Guidelines, and National Institute for Health and Care Excellence (NICE) all have position/guideline recommendations supporting CGM, none of these specifically discuss if and when I-CGM should be considered in the treatment paradigm.^6,31-33 The following position statements directly invoke I-CGM, but only discuss optimal patient selection criteria:

American Diabetes Association (ADA) – In the safety subheading of a 2022 clinical practice guideline published by the ADA Professional Practice Committee, the authors state that contact dermatitis has been associated with all CGM devices, often linked to isobornyl acrylate. In some patients who have sensitivities to the tape used with subcutaneous CGM patches, the authors comment that I-CGM may provide an alternative that could preclude dermatitis events.³⁴

European Association for the Study of Diabetes (EASD) – A consensus report published jointly by the EASD and the ADA in 2021 states that I-CGM could be a clinical alternative for patients who have sensitivities to the adhesive that is required with subcutaneous CGM.³⁵

American Association of Clinical Endocrinology (AACE) – In 2021, the AACE issued a Grade C recommendation that clinicians should ensure patients undergoing treatment with CGM do not ingest any substances that could interfere with reliable interstitial glucose readings.³² In the evidence section that informs this recommendation, Grunberger, et al. cite other CGM systems that are susceptible to inaccuracy when in the presence of acetaminophen, ascorbic acid, xylose, bilirubin, or uric acid. Conversely, this section reports that Eversense^® sensors are only vulnerable to inaccuracy in the presence of mannitol or tetracycline, consistent with the contraindications listed by the FDA packaging.³⁶

Other Expert Opinion

Deiss, et al. (2019) present a collection of consensus best practice recommendations by a panel of international clinicians who were involved with early Eversense^® clinical trials.³⁷ Among the best practices, the following considerations are mentioned in relation to optimal patient selection criteria:

• The authors note that the adhesive for Eversense^® does not contain isobornyl acrylate. Additionally, they also discuss how the daily changing of adhesive allows for regular skin care at the site. They conclude that both of these characteristics make I-CGM a viable alternative for patients with a history of skin reactions to adhesives.
• Deiss, et al. suggest that I-CGM is an ideal alternative to subcutaneous CGM for people who have an ongoing environmental risk to continued permanent breach of the skin, such as dust exposure.
• Deiss and colleagues mention the need for mobile device compatibility with the app, as well as ability to navigate the app. They then comment that certain groups of patients may be unable to access or use this technology and would not be suitable candidates for I-CGM.

This updated evidentiary review is being conducted to evaluate whether the published evidence base continues to support the equivalency of I-CGMs and traditional subcutaneous CGMs in the management of adult DM. The evidence suggests that for adult patients managing DM, I-CGM performs with little to no difference in diagnostic accuracy, patient-reported efficacy outcomes, objective efficacy measures, and device/procedure-related AE rate when compared to subcutaneous CGM. Furthermore, the evidence suggests that the optimal patient selection criteria for I-CGM and for subcutaneous CGM are largely overlapping. Although limited in quality, this evidence base is sufficient to determine noninferiority/equivalency between I-CGM and subcutaneous CGM.

Additionally, although no direct evidence was identified that assessed I-CGM utilization among non-insulin treated (NIT) patients with diabetes complicated by hypoglycemia, there is still adequate evidence to infer equivalence with subcutaneous CGM systems among this population based upon the totality of evidence. Firstly, among the approved indications for I-CGM, the FDA has cleared Eversense^® to “provide glucose trend information”, and to “provide alerts for the detection and prediction of episodes of low blood glucose (hypoglycemia) and high blood glucose (hyperglycemia)”.³⁸ Also, although outside of the scope of the main evidentiary review, 3 publications were identified via bibliographic cross-referencing that evaluated subcutaneous CGM benefit among this subgroup of patients. One of these 3 trials concluded that among NIT patients with DM complicated by hypoglycemia, subcutaneous CGM systems resulted in a significantly greater reduction in HbA1c than SMBG.³³ The other 2 studies suggested CGM systems were able to detect hypoglycemic events among NIT patients that were overwhelmingly undetectable by symptoms or SMBG.^39,40

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36. Grunberger G, Sherr J, Allende M, et al. American Association of Clinical Endocrinology clinical practice guideline: The use of advanced technology in the management of persons with diabetes mellitus. Endocr Pract. 2021;27(6):505-537.
37. Deiss D, Szadkowska A, Gordon D, et al. Clinical practice recommendations on the routine use of Eversense, the first long-term implantable continuous glucose monitoring system. Diabetes Technol Ther. 2019;21(5):254-264.
38. U.S. Food & Drug Administration (FDA). Approval Order - Eversense Continuous Glucose Monitoring System. Accessed 6/18/24.
39. Gehlaut RR, Dogbey GY, Schwartz FL, Marling CR, Shubrook JH. Hypoglycemia in type 2 diabetes - more common than you think: A continuous glucose monitoring study. J Diabetes Sci Technol. 2015;9(5):999-1005.
40. Munshi MN, Segal AR, Suhl E, et al. Frequent hypoglycemia among elderly patients with poor glycemic control. Arch Intern Med. 2011;171(4):362-364.

• Implantable continuous glucose monitors
• I-CGM