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36 Digitized Approaches to Diabetes Diagnostics and Therapeutics TADEJ BAT TELINO, JENNIFER L. SHERR, ALFONSO GALDERISI, AND KLEMEN DOVC CHAPTER OUTLINE Sensor Calibration and Accuracy, 1424 Improvements in Glycemic Outcomes in Type 1 Diabetes, 1439 CGM Technology Is Transformative for Diabetes Care, 1426 CGM Is Effective in Daily Management of T2D on CGM Data Make It Possible to Understand and Manage Insulin Regimens, 1440 Multiple Risk Factors in Diabetes, 1426 Use of CGM in People With T2D Not on Insulin Therapy, 1440 Making Daily Decisions Using CGM Technology, 1428 Telemonitoring and Telemedicine Are Essential Using CGM-Derived Glucose Metrics in Clinical Practice, 1430 Attributes of CGM Technology, 1440 Time in Range in T1D and T2D, 1430 Insulin Delivery, 1441 Time in Range in Elderly People With Diabetes and Connected Insulin Pens, 1441 Those at High Risk of Hypoglycemia, 1431 Insulin Pumps, 1442 Time in Range During Pregnancy, 1433 Sensor-Augmented Pump Therapy, 1443 Decision-Support Systems for Visualizing CGM Data and Automated Insulin Delivery, 1445 Beyond, 1434 Anticipated Developments for Insulin Delivery and Ambulatory Glucose Profile—A Graphical Tool for Automated Insulin Delivery, 1446 Reviewing CGM Data, 1436 Use of Diabetes Technologies in Special Situations, 1448 Using the Ambulatory Glucose Profile Report in a Future Directions, 1451 Systematic Way, 1437 Using CGM Improves Measures of Glycemia Compared to SMBG, 1437 KEY POINTS The use of continuous glucose monitoring (CGM) is Insulin delivery with continuous subcutaneous insulin transformative for diabetes management, improving infusion (CSII, insulin pump) improves glycemia, reduces glycemia, reducing acute complications, and improving acute complications, and improves quality of life. quality of life. Advanced hybrid closed-loop systems for automated insulin All individuals with diabetes, regardless of the diabetes type, delivery (AID) currently represent the most successful therapy modality, or stage of the disease, benefit from the treatment modality for individuals treated with insulin. use of CGM. Special considerations are important for different user The use of CGM-derived metrics such as time in range (TIR), populations, age groups, sick-day management, regular time below range (TBR), and time above range (TAR) facilitates sport activities, and in-hospital and intensive care treatment. day-today diabetes management, glycemic outcomes, and Better access to diabetes technologies for all individuals with quality of life. diabetes is paramount. Artificial intelligence decision-support systems (advisers) can Further technologic developments may improve facilitate the day-to-day use of CGM. user-friendliness, additionally increase automation, and Connected insulin pens (smart pens) can further facilitate improve long-term user experience and satisfaction. treatment with multiple daily injections and improve glycemic outcomes. 1423 Downloaded for SYED K KAZMI ([email protected]) at North West Anglia NHS Foundation Trust from ClinicalKey.com by Elsevier on September 16, 2024. For personal use only. No other uses without permission. Copyright ©2024. Elsevier Inc. All rights reserved. 1424 S ECT ION VI I I Disorders of Carbohydrate and Fat Metabolism W hile the development of insulin therapy vastly changed the course of diabetes management, technologic advances have allowed for more refined treatment methods. Diabetes technologies have of the sensor itself into the subcutaneous tissue (implantable).9 Glucose readings are transmitted wirelessly at intervals from 1 to 5 minutes to a reader, to a smartphone or smartwatch app, or, in classically been categorized as glucose monitoring devices and the case of automated insulin delivery (AID) systems, to an insulin delivery modalities. The advent of capillary glucose insulin pump (see Fig. 36.1). CGM devices that transmit glucose measurements allowed for optimiza - data only when the user actively scans their sensor with a reader tion of insulin doses, yet continuous glucose monitoring has pro- or smartphone app are referred to as intermittently scanned vided exponential expansion in the frequency of glucose measures, CGM (isCGM).8 thereby permitting better understanding of glucose dynamics Transcutaneous CGM sensors have wear times from 7 to 14 days, within an individual and proving an opportunity to have a more during which they are active and after which a new sensor is personalized approach to disease management. Similarly, insulin applied. Implantable systems currently transmit glucose data for delivery modalities have evolved from subcutaneous administra - up to 180 days before replacement. All glucose sensors have tion using vials and syringes to insulin pens followed by con - performance characteristics depending on the diﬀerent wear nected insulin pens and continuous subcutaneous insulin periods (early, middle, late), the reference glucose levels (high, infusion (CSII) pumps. The latter forms the basis of more - in-range, low), and the rate of glucose change.10–14 advanced diabe where insulin delivery is linked to sensor glucose tes technologies The first modern CGM devices were introduced in 2000 as a readings. diagnostic tool,15 providing 72 hours of retrospective data when Mirroring what has been seen with technologies used in daily life, calibrated with SMBG readings. These first systems were not there has been rapid evolution and iteration of diabetes approved for insulin dosing or other therapeutic adjustments. technologies, leading to an expanding arsenal of tools that can be However, the accuracy, utility, and size of CGM devices have used by people with diabetes to help them achieve glycemic improved dramatically since the first systems were used to assess targets. Further, glycemic targets are no longer based solely on glycemia and are now an important part of daily diabetes care. averages derived from glycated hemoglobin A1c (HbA1c); now the Several CGM devices are approved for making insulin-dosing and lived experience can be better approximated with continuous titration decisions with no need for a confirmatory SMBG test glucose data including understanding of time spent in various reading, so-called nonadjunctive use. glucose ranges to help guide care. The landscape of the digitized The widespread use of CGM technology in diabetes care, along approach to care of people with diabetes will be reviewed herein. with the substantial number of clinical trials that have validated their eﬃcacy and safety, have transformed the way people with Understanding and Applying Continuous diabetes and health care professionals now manage glycemic control.15a This does not simply apply to the many day-to-day Glucose Monitoring Technologies in Diabetes decisions possible using CGM technology, but also to the Routine monitoring of glucose is essential for people with evaluation of long-term glucose exposure, which has previously diabetes to see how various foods and exercise can aﬀect their been understood only in the context of the measurement of glucose levels and cause glycemic excursions, as well as to glycated hemoglobin (HbA1c). This rapid evolution of CGM understand the glycemic impact of daily stress and illness. For technology has been accompanied by the development of novel people with diabetes, particularly for those on insulin or measures of glycemic performance that can be used to assess insu-linotropic therapy, frequent glucose monitoring can help short-term patterns and trends in glucose, as well as provide them to predict and reduce the risk of hypoglycemia. Just as measures of long-term glycemic exposure that can be used important for people with diabetes is to minimize glucose alongside a recent HbA1c test result to understand risks for variability and periods of extended hyperglycemia with ketosis, complications of diabetes. along with risk for ketoacidosis. The standard of care for glucose monitoring has been the use of Sensor Calibration and Accuracy self-monitoring of blood glucose (SMBG) by finger-prick testing to evaluate glucose levels in capillary blood (Fig. 36.1).1 Even Most CGM sensors are factory calibrated,10 which eliminates the when performed multiple times daily, for example, a 7-point need for users to calibrate them using SMBG fingerprick tests, or profile before and after meals and once at night, a full they may require daily calibrations using SMBG fingerprick understanding of glycemic profiles can never be entirely captured tests.9,16 A third method of calibration requires users to enter a by this sparse sampling approach (Fig. 36.2). Unfortunately, for calibration code provided with each sensor, before sensor many people with diabetes, fingerprick lancing can be painful, application.17 Diﬀerences in calibration requirements may aﬀect and suboptimal engagement with SMBG can be a barrier to choice of CGM device for an individual, since user engagement achieving glucose targets.2,3 Thus, the recommended daily can be aﬀected,2 and unwillingness to perform SMBG due to frequency of SMBG testing is not achieved by most people with discomfort or poor technique may aﬀect CGM system accuracy.18 type 1 diabetes (T1D) or type 2 diabetes (T2D), which aﬀects Sensor accuracy has been known to vary immediately after glucose control and increases the risks for long-term application because of insertion-site trauma and reduced glucose complications of diabetes.4,5 As a consequence, wearable bioavailability.19–21 Similarly, pressure-induced sensor attenuation continuous glucose monitoring (CGM) technologies are has been noted during compression at the application site,22 for increasingly used in the management of people with diabetes, example, when sleeping prone. Current systems have adapted to particularly individuals receiving insulin therapy (see Fig. 36.1).6 these situations, and there is no evidence of harm as a Commercially available CGM devices measure glucose levels in consequence in adults. However, use of CGM systems in acute the interstitial fluid in the subcutaneous space,7,8 either using a neonatal care must be cognizant of these, as described later. sensor with a thin filament inserted through the skin into the The accuracy of interstitial fluid glucose sensor readings is assessed subcutaneous space (transcutaneous; Fig. 36.3) or by insertion by regulatory authorities by comparison with blood Downloaded for SYED K KAZMI ([email protected]) at North West Anglia NHS Foundation Trust from ClinicalKey.com by Elsevier on September 16, 2024. For personal use only. No other uses without permission. Copyright ©2024. Elsevier Inc. All rights reserved. CHAPTER 36 Digitized Approaches to Diabetes Diagnostics and Therapeutics 1425 Capillary blood glucose measurements Capillary blood glucose measurements + Insulin syringes/pens + Insulin pumps* Capillary blood glucose Tubed insulin pumps Insulin Pens are pre-filled with monitoring provides point in reservoir is inside the pump insulin and eliminate the time measurements of hardware, connected to the need to draw up insulin current glucose levels infusion site via catheter made of steel or synthetic polymer tubes Patch insulin pumps Continuous glucose monitors Insulin is held within a Continuous glucose monitors + Insulin pumps reservoir placed directly on + Insulin pens the skin with a separate Current CGM devices measure polymer catheter inserted glucose in interstitial fluid every subcutaneously 1-5 minutes. Automated insulin delivery Continuous glucose monitors CGM sensor data are + Insulin smart pens communicated to an algorithm, Smart Pens record and which adjusts insulin delivery store insulin doses and via the insulin pump to match timings. These can be glucose levels reviewed on the pen and are also sent to the CGM system CGM, continuous glucose monitoring Fig. 36.1 The evolution of diabetes technology in glucose management in diabetes. SMBG glucose snapshots CGM glucose daily profile Glucose Glucose level level (mmol/L) (mmol/L) 10 10 3.9 3.9 12am Noon 12am 12am Noon 12am Fig. 36.2 CGM sensor glucose readings provide a meaningful proﬁle of daily glucose levels and ﬂuctuations. SMBG testing provides isolated snapshots of glucose levels at any one moment of time. Most people would not perform ﬁngerstick testing eight times daily as shown in the left graphic, and both high and low glycemic excursions may not be detected. In contrast, CGM sensors collect glucose readings minute-by-minute to generate a complete view of glucose levels throughout the day and through the night (right), covering periods of high or low glucose, as well as peaks and troughs when glucose is variable. Transcutaneous CGM sensor glucose readings taken concurrently and measured using a reference blood glucose analyzer. Sensor accuracy is quantified by metrics that focus on the mean absolute relative diﬀerence Skin (MARD) between a CGM measurement and the corresponding Cells simultaneous value obtained by the reference system. Currently available CGM devices achieve MARD values in the range of 8% to 14%,10,11,14 which compares well with the wide accuracy range Interstitial fluid of SMBG test meters.23 Among CGM devices, those that are approved for nonadjunctive insulin dosing and titration, or use Glucose with AID systems, typically have lower MARD values of below 10%.10,11,24 However, no prospective clinical studies have shown Capillary blood this to be a requirement and the exact clinical significance of lower Fig. 36.3 Transcutaneous CGM sensors measure glucose in the MARD has not been fully evaluated. interstitial ﬂuid. Glucose in the capillary blood diffuses into the interstitial Since blood and interstitial fluid are diﬀerent physiologic ﬂuid in the subcutaneous space below the epidermis. Transdermal CGM compartments with diﬀerent glycemic dynamics,25 the sensors detect the glucose in the interstitial ﬂuid using electrochemical concordance between interstitial fluid glucose and blood glucose via insertion of a thin ﬁlament. readings must also take into account the time it takes for blood glucose levels to Downloaded for SYED K KAZMI ([email protected]) at North West Anglia NHS Foundation Trust from ClinicalKey.com by Elsevier on September 16, 2024. For personal use only. No other uses without permission. Copyright ©2024. Elsevier Inc. All rights reserved. 1426 S ECT ION VI I I Disorders of Carbohydrate and Fat Metabolism be reflected in the interstitial fluid. The average time-lag may vary proportion to average blood glucose levels, it is influenced by a from 3 to 15 minutes,10–14 but may be higher when the range of nonglycemic factors related to blood-cell turnover and physiologic rate of change of glucose between compartments is homeostasis.29 Thus, HbA1c can either overestimate or in more above 2.0 mg/dL/min (0.1 mmol/L/min). clinical conditions underestimate average glucose in any person A further test of system accuracy and precision is the consensus with diabetes. Use of CGM systems has confirmed this can create error grid,26 which evaluates the clinical significance of a risk of treatment overintensification for people in whom HbA1c inaccuracies in sensor-glucose readings and assigns a specific level tends to overestimate their average glucose exposure,30 with of risk to any errors within defined zones, based on whether these consequent increase in risk of hypoglycemia. have an impact on clinical decision making. For example, the most clinically important error would be a high CGM reading leading to insulin administration in the setting of a low CGM Data Make It Possible to physiologic glucose, furthering the risk of severe hypoglycemia. A snapshot summary of characteristics for CGM systems available at Understand and Manage Multiple the time of writing is provided in Table 36.1. Risk Factors in Diabetes Although HbA1c has allowed us to understand the long-term CGM Technology Is consequences of hyperglycemia, we now know it is just as Transformative for Diabetes Care important to avoid hypoglycemia and limit glucose variability. This CGM-driven approach to diabetes management has been A person with diabetes can measure their glucose levels at any termed the “triangle of diabetes care” (Fig. 36.5) and builds on the point during the day using a fingerprick SMBG test, but this can understanding that the frequency of hypoglycemia and degree of be painful,3 and it is hard to manage more than a few tests each glucose variability are independent risk factors in diabetes. day at recommended times. Equally, although HbA1c is a A meta-analysis of five landmark studies, the UKPDS,31 Action to well-established marker for long-term complications of diabetes, it Control Cardiovascular Risk in Diabetes (ACCORD),32 Action in is not a useful indicator of day-to-day glucose levels and Diabetes and Vascular Disease: Preterax and Diamicron Modified fluctuations. CGM technology is now able to provide objective Release Controlled Evaluation (ADVANCE),33 Veterans Aﬀairs information across all time periods of interest in diabetes Diabetes Trial (VADT),34 and PROspective pioglitAzone Clinical management. Trial In macroVascular Events (PROactive)35 trials, has shown intensive control of HbA1c has cardiovascular benefits, but without The Limitations of SMBG Testing improving overall mortality in people with T2D.36 Moreover, a Fingerprick SMBG tests provide isolated snapshots of glucose number of studies have shown that the relationship between levels at any one moment of time, whereas CGM sensors collect HbA1c and complications and/or mortality is not a straight line information to give the user and health care professionals a but takes a U-shaped or J-shaped curve,37 suggesting a lower complete view of glucose levels throughout the day, including HbA1c is not always better. In T1D, a 2018 study on 33,915 through the night, covering periods of high or low glucose, and individuals from the Swedish national diabetes registry reported peaks and troughs when glucose is variable (see Fig. 36.2). that people with T1D and an optimal HbA1c of ≤6.9% (or 52 mmol/mol) have a twofold risk of death from any cause or from cardiovascular disease compared to people without diabetes.38 In The Limitations of HbA1c order to control for variables not related to diabetes, the study HbA1c is an accepted measure of overall glucose control over the paired each person with T1D with five control subjects matched past 3 months and illustrates how a person with diabetes has been for age and sex, but without diabetes. The outcomes indicated that managing their treatment regimen. HbA1c was first associated achievement of gly-cemic targets for people with T1D is masking with diabetes in 1969,27 and it became clear there was a additional factors that contribute to increased risk of relationship between HbA1c, mean fasting glucose, and mean cardiovascular complications. daily glucose. Using HbA1c as a longitudinal marker of average The Need to Manage Hypoglycemia blood-glucose levels, the United Kingdom Prospective Diabetes Study (UKPDS) and the Diabetes Complications and Control The adverse consequences of hypoglycemia are an acknowledged Trial (DCCT) both showed that improved diabetes control, as part of diabetes therapy with insulin and insulinotropic drugs (see measured by HbA1c, reduces the risk of long-term health also discussion “Time in Range in Elderly People With Diabetes problems such as retinopa-thy, nephropathy, neuropathy, or and Those at High Risk of Hypoglycemia” later in this chapter). kidney failure.4,5,28 Based on these and subsequent studies, HbA1c The neurologic consequences include impairment of cognitive has become established as an objective measure of glycemic function, with confusion, irrational behavior, and drowsiness, and control and also the gold standard marker for risk of morbidity may ultimately lead to seizures and coma. People with diabetes and mortality for people with diabetes. Improving the HbA1c level may experience social or workplace embarrassment, as well as of a person with diabetes is important, and this is a proven physical injury.39 Acute hypoglycemia has been estimated to strategy for supporting long-term health in people with T1D or account for up to 10% of deaths in people with T1D under the T2D. As a glycemic marker, HbA1c does reflect average glucose levels age of 40 years.40 over a 2- to 3-month timeframe but cannot reflect the realities of There are clear strands of evidence that link hypoglycemia with day-to-day glucose levels and fluctuations. For example, people cardiovascular disease being associated with an increase in cardiac with diabetes who have identical HbA1c test results can have very dysrhythmia,41–43 increased inflammatory responses with diﬀerent patterns of hyperglycemia and hypoglycemia, which will endothelial-cell dysfunction that predisposes to aﬀect their treatment needs (Fig. 36.4). A further issue with atherosclerosis,44,45 and a disruption in the coagulation system HbA1c is that, although it is formed in red blood cells in that leads to a pro-thrombotic environment.46,47 Downloaded for SYED K KAZMI ([email protected]) at North West Anglia NHS Foundation Trust from ClinicalKey.com by Elsevier on September 16, 2024. For personal use only. No other uses without permission. Copyright ©2024. Elsevier Inc. All rights reserved. CHAPTER 36 Digitized Approaches to Diabetes Diagnostics and 1427 Therapeutics TABLE 36.1 Attributes of Glucose Sensors Used by Available CGM Systemsa Wear Type of Time Separate Warm-up Scanning Device Sensor Calibration (Days)d Wear Site Alarms Transmitter Period Needed Abbott FreeStyle Transdermal Factory 14 Back of upper arm No No 60 min Yes Libre systemb calibrated Abbott Transdermal Factory 14 Back of upper arm Optional high No 60 min Yes FreeStyle Libre calibrated and low glucose 2 systemb Abbott Transdermal Factory 14 Back of upper arm Optional high No 60 min No FreeStyle Libre calibrated and low glucose 3 systemb Dexcom Onec Transdermal Factory-supplied 10 Back of arm, Optional high Yes 2 hr No calibration code abdomen, buttocks and low glucose (age 2–17 yr) Dexcom G4 & Transdermal Twice-daily 7 Back of arm, High and Yes 2 hr No G5c SMBG test abdomen, buttocks low alerts (age 2–17 yr) Dexcom G6c Transdermal Factory-supplied 10 Back of arm, High and Yes 2 hr No calibration code abdomen, buttocks low alerts (age 2–17 yr) Predictive Dexcom G7c Transdermal Factory-supplied 10 Back of arm, High and No 30 min No calibration code abdomen, buttocks low alerts Predictive Medtronic Transdermal Twice-daily 7 Abdomen, back High and Yes 2 hr No Guardian SMBG test low alerts Connectd Predictive Medtronic Transdermal Twice-daily 7 Back of arm, High and Yes 2 hr No Guardian 3 SMBG test abdomen, buttocks low alerts (age 7–13 yr) Predictive Medtronic Transdermal Factory 7 Back of arm, High and Yes 2 hr No Guardian 4 calibrated abdomen, buttocks low alerts Predictive Medtronic Transdermal Factory 7 Back of upper arm High and No 2 hr No Simplera calibrated low alerts Predictive Roche Implantable Twice-daily 180 Implanted under Optional high Yes 24 hr No Senseonics SMBG test skin on the upper and low glucose Eversense E3e arm aThese systems reflect those used most frequently in clinical studies in T1D and T2D. Other CGM systems are available. bAll FreeStyle Libre systems, https://www.diabetescare.abbott/support/manuals/uk.html cAll Dexcom Mobile systems, https://www.dexcom.com/en-us/guides dhttps://www.medtronicdiabetes.com/customer-support/guardian-connect-system-support ehttps://www.ascensiadiabetes.com/eversense/user-guides/ The table shows the product range for the manufacturers with widely used standalone CGM products. SMBG, self-monitoring of blood glucose. The Need to Manage Glycemic Variability high glucose levels.48–50 Moreover, in people with diabetes who are admitted to hospital for any clinical reason, glycemic swings The link between glucose variability and cardiovascular have been shown to be associated with both increased mortality pathology has been strengthened by the availability of CGM and longer hospital stay.51 CGM data have also indicated a data. In both T1D and T2D, experimentally induced swings correlation between reactive oxygen metabolites and glucose from hypoglycemia to hyperglycemia cause significant increases variability in T2D,52,53 in which increased reactive oxygen in endothelial dysfunction and oxidative stress compared to metabolites were significantly correlated with the mean sustained amplitude of glucose Downloaded for SYED K KAZMI ([email protected]) at North West Anglia NHS Foundation Trust from ClinicalKey.com by Elsevier on September 16, 2024. For personal use only. No other uses without permission. Copyright ©2024. Elsevier Inc. All rights reserved. 1428 S ECT ION VI I I Disorders of Carbohydrate and Fat Metabolism HbA1c 62 mmol/mol HbA1c 62 mmol/mol (7.8%) (7.8%) Glucose Glucose level level (mmol/L) (mmol/L) 10 10 3.9 3.9 12am Noon 12am 12am Noon 12am Fig. 36.4 Continuous glucose monitoring sensor readings provide a meaningful proﬁle of daily glucose levels and ﬂuctuations. CGM sensor data reveal the important details in daily and weekly glucose patterns that are unique to each person with diabetes, even if they have identical HbA1c test results. Dexcom G7 system FreeStyle Libre system Improve overall glucose levels (HbA1c) Better outcomes for people with diabetes Limit Avoid glucose hypoglycemia variability Fig. 36.5 Triangle of diabetes care—a model for application of CGM in diabetes care. The triangle of diabetes care illustrates how the attributes of CGM technology can be used to manage multiple risk factors in diabetes. Fig. 36.6 Examples of CGM trend arrow displays. Images show the smartphone home-screen representation of current glucose and the associated rate of change trend arrow for two CGM systems currently excursions each day and with the mean diﬀerences in glucose approved by regulatory authorities for nonadjunct use to make insulin between days. dosing decisions. The Dexcom G7 system shows that glucose is falling rapidly at >2.0 mg/dL (>0.1 mmol/L) and is predicting low glucose; the FreeStyle Libre system shows that glucose is rising at 1.0–2.0 mg/dL Making Daily Decisions Using (0.06–0.1 mmol/L). See Table 36.2 for all trend arrow rates of change. CGM Technology Trend Arrows and Projected Glucose The first major benefit for people with diabetes using CGM devices is the impact on eﬀective daily diabetes self-management CGM technology is able to collect glucose readings on a decisions. Being able to see current glucose levels on demand, at minute-by-minute basis, and each system is able to calculate any time of day or night, without the need for fingerprick SMBG both the direction and the rate of change of glucose based on the testing, ensures CGM users are more aware of their glucose status. readings stored over the previous 15 minutes. This information However, on its own, a high or low glucose reading can prompt a is displayed on the CGM reader or smartphone app as a trend person with diabetes to take corrective action that may or may not arrow, showing whether glucose levels are rising, falling, or be needed. A more-significant capability with CGM devices is that stable. In addition to the direction of change, the trend arrow these systems also provide trend arrow information on the indicates to the user how fast their glucose is rising or falling. By direction and rate of change of glucose (Fig. 36.6). looking at the trend arrow displayed alongside their current glucose Downloaded for SYED K KAZMI ([email protected]) at North West Anglia NHS Foundation Trust from ClinicalKey.com by Elsevier on September 16, 2024. For personal use only. No other uses without permission. Copyright ©2024. Elsevier Inc. All rights reserved. CHAPTER 36 Digitized Approaches to Diabetes Diagnostics and 1429 Therapeutics TABLE 36.2 Comparison of the Rates of Change That Are Illustrated by the Trend Arrow Displays of Diﬀerent CGM Providers Trend Arrows Number and Abbott FreeStyle Libre Medtronic Guardian Connect, Roche Senseonics Orientation Systema Dexcom G4/G5/G6/G7 Mobileb Sensor 3, Sensor 4c Eversensed NA NA >3 mg/dL 0.2 mmol/L NA per minute NA >3 mg/dL >0.2 mmol/L 2-3 mg/dL 0.1–0.2 NA per minute mmol/L per minute >2 mg/dL 2–3 mg/dL 0.1–0.2 1–2 mg/dL 0.05–0.1 >2 mg/dL >0.1 mmol/L per minute mmol/L per minute mmol/L per minute >0.1 mmol/L per minute 1–2 mg/dL 1–2 mg/dL NA 1–2 mg/dL 0.05–0.1 0.05–0.1 mmol/L per minute 0.05–0.1 mmol/L per minute mmol/L per minute 0.1 mmol/L per minute mmol/L per minute mmol/L per minute per minute NA >3 mg/dL >0.2 mmol/L 2-3 mg/dL 0.1–0.2 NA per minute mmol/L per minute NA NA >3 mg/dL >0.2 mmol/L NA per minute aAll FreeStyle Libre systems, https://www.diabetescare.abbott/support/manuals/uk.html bAll Dexcom Mobile systems, https://www.dexcom.com/en-us/guides chttps://www.medtronicdiabetes.com/customer-support/guardian-connect-system-support dhttps://www.ascensiadiabetes.com/eversense/user-guides/ The table shows the product range for the manufacturers with widely used standalone CGM products. These systems also reflect those used most frequently in clinical studies in T1D and T2D. Other CGM systems are available. reading, CGM users can make an informed and timely decision Evolution of the “Slide Rule” System for on whether to take any corrective action to adjust their glucose levels, for example, by taking insulin or intake of carbohydrates Using Trend Arrows for Insulin Dosing in order to prevent unwanted rise or fall in glucose During the Juvenile Diabetes Research Foundation (JDRF) and concentration. This also allows them to understand the context Diabetes Research in Children Network Study Group (DirecNet) of their glucose levels and trends and to make decisions about studies on CGM,54,55 participants had been advised that, based on timing of exercise, meals, and glycemic management during their trend arrows and current glucose reading, they should increase illness. Table 36.2 describes characteristics of trend arrows or decrease their regular insulin dose by 10% (glucose rising or displayed by the most widely used standalone CGM products falling) or 20% (glucose rising rapidly or falling rapidly). However, that have been more commonly used in clinical studies in T1D subsequent patient-reported data revealed that an upward trend and T2D. arrow might trigger a self-determined insulin dose increase of more Making Insulin Dosing Decisions than 100% of their usually calculated dose, whereas a downward trend arrow might result in an insulin dose reduction of up to Incorporating Glucose Trend Arrows 50%.56 Consequently, more-specific recommendations were developed, in As discussed, multiple CGM devices are approved by health which a defined glucose concentration value was added or authorities for making decisions on insulin dosing, without the subtracted to adjust the current glucose level, depending on the need for a confirmatory SMBG test. Recommendations for trend arrow displayed.57 However, this creates additional burden treatment decisions should take into account both the on CGM users, requiring mathematical skills and a level of direction of the trend arrows and the diﬀerent rates of change. numeracy. Even when simplified,58 this approach did not take into There is no standardization between diﬀerent CGM devices account clinical factors, such as individual insulin regimens or regarding trend arrow orientations and rate of change; thus, insulin sensitivity. recommendations for insulin dosing must be adjusted to To accommodate as many factors as possible into the dosing accommodate the distinctions of diﬀerent CGM devices. To decision, a selection of “slide rule” approaches have been defined. date, there have been several recommendations published for Laﬀel et al59 and Aleppo et al60 published tables guiding the how to respond to trend arrow information for insulin dosing addition or subtraction of a fixed amount of insulin based on the in T1D, as discussed next. glucose trend arrow orientation and rate of change, but Downloaded for SYED K KAZMI ([email protected]) at North West Anglia NHS Foundation Trust from ClinicalKey.com by Elsevier on September 16, 2024. For personal use only. No other uses without permission. Copyright ©2024. Elsevier Inc. All rights reserved. 1430 S ECT ION VI I I Disorders of Carbohydrate and Fat Metabolism FreeStyle Dexcom G5/G6 ISF Insulin FreeStyle Dexcom G5/G6 ISF 70-180 mg/dL >180-250 mg/dL >250 mg/dL Libra App Receiver (mg/dL) units Libra App Receiver (mg/dL) Insulin units Insulin units Insulin units

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