By Gerri Klein RN MScN (biography and disclosures)
What I did before
Before the times of COVID and the introduction of continuous glucose monitoring, as a nurse diabetes educator, I instructed patients living with diabetes to attend the lab between 2 to 4 times per year to have glycated hemoglobin (A1C) assessment. In addition, I recommend home blood glucose monitoring at various times throughout the day for all patients who live with diabetes. Patients on insulin were instructed to perform as many as 6 to 8 finger pokes per day, while those not on insulin were asked to do less.
What changed my practice
A1C assessment became the gold standard of care for Canadian citizens living with diabetes when Diabetes Canada (formerly known as the Canadian Diabetes Association) included this laboratory test in the first published clinical practice guidelines for the treatment of diabetes mellitus in 1992 (1). Although mentioned in the initial 1992 standards of care, the use of home blood glucose monitoring, using finger sticks with a lancing device was not widely accepted in the early part of that decade. In contrast, the 1998 Canadian standards of care promoted home blood glucose monitoring as an “essential” part of the treatment plan for those with type 1 diabetes, and “integral” for persons with type 2 diabetes treated with oral hypoglycemic agents when used in conjunction with regular A1C testing (2).
While widely used and relied upon, there are many pitfalls when using these glycemic measures to guide treatments (3; 4). Although literature states that A1C levels reflect blood glucose values over a three-month period, glycation of red blood cells within an immediate 30-day period prior to the blood test has a more significant effect on the A1C value than does glycosylation of red blood cells aged 90–120 days. As the A1C is an average of the person’s glycemic control, it could be hiding many hyperglycemic and hypoglycemic excursions. A1C testing has been found to be inaccurate in persons with low hemoglobin, or vitamin B-12 and folate deficiency anemias and for those with kidney disease; may not be reliable in pregnancy, and should not be used after a recent blood transfusion or for persons experiencing alcoholism. A1C results are affected by some medication consumption, such as Vitamin A and C, antibiotics such as penicillin or cephalosporins, and medications such as salicylates and opioids. A1C testing requires persons living with diabetes to attend a laboratory, a difficult task for the last several months during COVID lockdowns. Lastly, A1C does not provide sufficient information to adequately inform immediate/short-term treatment decisions (5).
When first introduced, home blood glucose meters (HBGM) made real-time monitoring, and therefore intensive management, possible for persons who live with diabetes. However, the information offered by these devices is painful to obtain due to the necessity of finger pricks and is narrow in scope. Many will not test enough times during the day to get a complete picture of the blood sugars in order to make fully informed treatment decisions (6). As well, HBGM readings give time-limited information on which to base decisions. Present blood sugar is given, but there is no indication about where the blood sugar has been, or where it is trending.
In the past decade, continuous glucose monitors have changed diabetes care. Real-time continuous glucose monitors (rtCGMs) use a sensor, applied to skin and worn for 10 to 14 days to assess interstitial fluid glucose 24-hours per day, 7 days a week. rtCGM sensors communicate with readers using Bluetooth technology as long as the sensor is within range of the reader. Intermittently scanned continuous glucose monitors (isCGMs) have a similar ability as the rtCGM, but require the user to swipe a reader across the sensor to obtain data. rtCGMs and some isCGMs have high/low alerts to notify users when their blood sugars are dangerously high or low, a valuable tool for those on hypoglycemic medication, particularly those with hypoglycemic unawareness. Due to the time that it takes for glucose to diffuse from blood into the interstitial fluids, the data offered by either type of CGM may not be as current as offered by an HBGM. CGM users are advised to confirm readings with an HBGM if physical symptoms do not coincide with the CGM data.
Recent updates in the Diabetes Canada clinical practice guidelines include recommendations for use of A1C assessments as well as rtCGMs and isCGMs (5). In the recently revised guidelines, 2021, A1C assessments are recommended every 3 months, “Grade D, Consensus level” of confidence. Diabetes Canada has given a “grade A, Level 1A” recommendation for rtCGM for persons living with type 1 diabetes to reduce A1C and increase TIR (time in range), and significantly reduce duration and incidence of hypoglycemia; and to improve quality of life. A “grade B, Level 2” recommendation has been given for isCGM to increase TIR, reduce frequency and duration of hypoglycemia, and improve treatment satisfaction.
CGM glucose metrics include TIR (time in range), TAR (time above range), TBR (time below range), as well as glycemic variability (standard deviation of readings). These metrics make it possible for healthcare providers to set individualized blood glucose targets for patients and to conveniently track the data.
Patients can download their data using a free, industry-supported app and email their data to healthcare providers prior to visits. If the volume of emails is a concern for practitioners, or if patients do not send their data when asked, healthcare providers can log into industry-supported pages for remote monitoring or discuss glucose control with patients during a visit. Day to day blood glucose graphs, along with the amount of time that blood glucose is within a specified target range, frequency and duration of hypo/hyperglycemic events, including timing of these events, standard deviation of blood sugar data, and glucose averages for times during the day are all available online, making it easier for healthcare providers to devise appropriate treatment plans. An estimated A1C is also provided.
What I do now
For all my patients who are on hypoglycemic medications, oral or injectable, I suggest using rtCGM or isCGM. Cost is a significant issue for many although the cost of these devices varies from pharmacy to pharmacy. BC Fair Pharmacare does cover the cost of some rtCGMs if the person has special authority (obtained by a physician and when the person is on two types of insulin or an insulin pump) and has paid their deductible. Other provincial pharmacare plans cover both rtCGMs and isCGMs for qualifying patients. For those without app-compatible phones, some companies provide readers free of charge with proof of sensor purchase. In BC, only rtCGMs are included on the Fair Pharmacare formulary and therefore if the person’s deductible is too high for Fair Pharmacare rtCGM coverage they must pay out of pocket. If unable, I suggest using an isCGM as these devices can give the same data as rtCGM at much less cost.
Even intermittent use or a short trial of 10 days to two weeks with either of these devices can be enlightening for patients. To get them started, I instruct my patients to contact companies directly, as frequently sample devices are offered at no cost. Some companies have compassionate care programs to supply sensors free of charge or at a reduced cost, physicians must apply to the company for patients to access these programs.
With the ongoing COVID restrictions, many of my patients have been unable (or unwilling) to obtain an A1C from a lab test. In my practice, I have found it helpful to use glucose TIR to assess glucose control as an adjunct measure to A1C results; when an A1C is not available; and to guide treatment recommendations. Treatment and goals can be customized to patients as TIR is determined by age, physical status, co-morbidities, length of time living with diabetes, living situation; and hypoglycemic awareness (5;6;7).
There have been momentous discoveries in diabetes care over the past 100 years that have improved the lives of those living with diabetes. I believe that the discovery of CGM is pivotal and will significantly change outcomes for many who live with the condition. As cost will be a barrier for many, it is beholden upon us as healthcare providers to lobby our provincial health ministries to make these devices available to all who are on hypoglycemic medication, particularly insulin, and in the future to anyone who lives with diabetes and needs to perform home glucose monitoring.
Resource:
Special Authority Request — Continuous Glucose Monitoring System. BC Ministry of Health. (Download PDF). More info: gov.bc.ca/pharmacarespecialauthority.
References:
- Expert Committee of the Canadian Diabetes Advisory Board. Clinical practice guidelines for treatment of diabetes mellitus. CMAJ. 1992;147(5):697-712. (View)
- Zinman B, Lau D, Leiter L, Meltzer S, Daneman D, et al. 1998 clinical practice guidelines for the management of diabetes in Canada. CMAJ; 1998;159 Suppl 8(6): S1-29. (View)
- Radin M. Pitfalls in Hemoglobin A1c Measurement: When Results may be Misleading. J Gen Intern Med. 2014; 29(2): 388–394. DOI: 10.1007/s11606-013-2595-x. (View)
- Kaiafa G, Veneti S, Polychronopoulos G, et al. Is HbA1c an ideal biomarker of well-controlled diabetes? Postgrad Med J. 2021; 97(1148): 380–383. DOI: 10.1136/postgradmedj-2020-138756. (View)
- Diabetes Canada Clinical Practice Guidelines Expert Working Group: Cheng A, Feig D, Ho J, Siemens R. Blood Glucose Monitoring in Adults and Children with Diabetes: Update 2021. Can J Diabetes. 2021; 45(7); 580-587. DOI: 10.1016/j.jcjd.2021.07.003. (View)
- Holt R. et al. The management of type 1 diabetes in adults. A consensus report by the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASE). Diabetes Care. 2021; 64(12): 2609-2652. DOI: 10.2337/dci21-0043. (Request with CPSBC or view with UBC)
- Gabbay M, Rodacki M., Calliari L, et al. Time in range: a new parameter to evaluate blood glucose control in patients with diabetes. Diabetol Metab Syndr. 2020; 12(22). DOI: 10.1186/s13098-020-00529-z. (View)
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Thank you Gerri. This is an important topic, and I appreciate your summary of this as well as your inclusion of situations that can skew HgA1c results
Thank you for a good summary of the pitfalls of home blood glucose monitoring. However, I don’t think these expensive monitors are necessary for all diabetics on any medication. I have found that for a significant number of diabetic patients on oral medications HBGM does not improve their glycemic control, and becomes an unnecessary item of focus, it is also costly. For these patients, CGM is another layer of unnecessary and expensive technology. I agree that for Type 1 Diabetics and Type II on Insulin, especially multi dose insulin, or folks with difficulty controlling sugars CGM may be helpful. I think we need to be discerning about which type of monitor is most appropriate for which patient.
I am suspicious about the benefits of the technology providing warning about hypoglycaemia, having been called out recently in the middle of the night to administer glucagon to a patient with a CBM, with very low blood sugars. When he perked up he was far more concerned with repeatedly checking his sugars than with eating the sandwich he had been given to keep his sugars up! His monitor had apparently NOT warned him about his low sugar.
Thank you for your response. These are expensive monitors. And not necessary for all persons on any medication. However, as a teaching tool to show how the other elements of treatment, diet, and exercise affect blood sugars these devices are very revealing. If a patient is willing and able to test pre/post-meal and exercise, they can get the same information. But many patients are unwilling or unable. All of the companies provide at least one sample free of charge. When patients use a CGM, even for a short time, they learn where their high blood sugars are coming from, and in many cases take steps to change to avoid those spikes, thereby delaying or avoiding intensifying management. Conversely, patients often see the benefits of their actions, such as taking a walk, using a CGM for a short time.
There are issues when blood sugars fall rapidly. CGMs measure interstitial fluid, not blood glucose. Patients need to have a blood glucose monitor on hand to check a CGM reading that is lower than expected or does not match the way he/she is feeling.
Thank you for this succinct and excellent review. Understanding which sensors can provide accurate alerts and predict impending low glucose is an important piece for health care providers to understand. As you point out different sensors have different features. It is important to match what is available to the needs of the person with diabetes.
Until we see actual all-cause mortality reduction with these devices in patients with type 2 diabetes, there is no good evidence to proceed with these very expensive interventions.
Thank you for your comment. The use of rtCGM is recommended for those on basal-bolus insulin or pump therapy regardless of their diagnosis of type 1 or type 2 (Grade A, Level 1A). While you are correct in stating that studies have not determined actual all-cause mortality reduction for people living with type 2 diabetes with these devices, the updated guidelines suggest rtCGM or isCGM could be offered to those with type 2 who have not attained their goal A1C as an alternative to home blood glucose finger poke testing, if preferred by the individual as part of training, education and support in self-management. (http://guidelines.diabetes.ca/cpg/chapter-9-2021-update).
Partly I wonder what the objective is with continuous glucose monitoring? Does it improve any patient-relevant end-points? Certainly it’s fascinating, and I’d be curious too, but I’m betting the average patient (and provincial health ministry) would reap greater benefits if the money spent on such a device were instead spent on healthy foods and physical activity?
Treatment for diabetics continues to change and improve — thank you for the update.
I wonder, now that rtCGMS has been around for a while, and pumps can give insulin based on those interstitial sugar readings (Medtronic for ex), are there any statistics on frequency of Errors, where the pump gives more insulin and causes significant hypoglycemia? This has been a safety concern to me.
As a T1DM here are my thoughts:
When my blood glucose is steady the result from my CGM and from a fingerstick will match.
CGM has helped me identify which foods cause me the most difficulty (generally it’s foods with a high glycemic index _but_ not exclusively)
I personally focus as much on time in range as GMI
I have disabled hyperglycemia warnings because they can be annoying and I’m monitoring it closely in those circumstances anyway.
I have a friend who found it to be too much information and started to fiddle too much with her pump causing her to swing more widely. She went back to fingersticks.
One of my challenges with my CGM is the time lag reflecting changes in my blood glucose after oral intake. For instance if I drink OJ to correct hypoglycemia it can sometimes take up to 10 minutes for the change to be reflected on my CGM since it measures interstitial fluid.
Thanks, everyone for the comments. It is always a discussion as to where scare public monies should be spent? On prevention or on treatment? Yes, prevention is better than treatment, but once the condition has arisen, treatment is essential. And while healthy foods and activity are essential elements of diabetes management, no amount of healthy diet or exercise prevents type 1 diabetes. And for some folks with type 2 diabetes, diet and exercise were not the issues.
The use of CGMs either rtCGM or isCGM has been linked with dramatically improved patient-relevant endpoints, including reducing A1C. The duration and incidence of hypoglycemia is reduced particularly severe hypoglycemia. Patients report improved quality of life. Parents of children using CGM reported a “high degree of satisfaction” with this type of glucose monitoring.
http://guidelines.diabetes.ca/cpg/chapter-9-2021-update
I am only including one reference, although there is a wealth of literature to support these claims.
Cost of CGMs is an appropriate concern. Healthcare dollars are scarce, and everyone needs to be mindful of how expensive recommendations are to the public purse and to our patients’ pockets as well. Home blood glucose monitoring is expensive. If done as often as is necessary to get a complete picture of blood glucose excursions, the cost would be more than an isCGM, and oftentimes about as expensive as rtCGM. And that does not include expenses for complications. A trip to the emergency room for a hypoglycemic event is far more expensive than the annual cost of a rtCGM. Although CGMs have been in existence for a number of years, there has been a delay in assessing the financial benefits of using CGMs for glucose assessments in the prevention of long-term complications. However, if we look to the benefits that occurred with blood glucose monitoring, and the reduction in complications, and therefore costs to the healthcare system, it is likely that the reduced costs for treatment for complications will far outweigh the upfront costs of CGMs for those on insulin.
Thank you for your question about errors and stats on closed-loop insulin pumps. There is a wealth of literature on errors in these systems, although very few on times when the pump delivers more insulin based on blood glucose readings from the rtCGM. For the most part, errors are found from sensor malfunction or site infusion failures. The sensor simply stops reading the interstitial fluid glucose or the site is no longer absorbing and therefore the insulin does not deliver insulin resulting in hyperglycemia. Inaccurate carb counting has also been named as a reason for high/low blood sugars. Many persons wearing rtCGM experience alarm fatigue, and turn off the high/low alarms, causing issues with control.
As a btw, few pumps are connected to the CGMs. However, there is a significant grassroots movement, called “#we are not waiting,” a DIY movement that has created a closed or semiclosed looping mechanism with a CGM to an Omnipod pump. If you attended the Diabetes Conference in November 2020, Dr. Peter Senior and Kate Farnsworth presented on this topic. The Lancet recently published a consensus statement for DIY looping. https://www.thelancet.com/journals/landia/article/PIIS2213-8587(21)00267-9/fulltext
Unfortunately, the author of this piece receives direct payment from Sanofi, who are manufacturers of continuous glucose monitors (eg https://www.news.sanofi.us/press-releases?item=127726)
I have to agree with Amy and Noel’s points; some papers show statistical improvement in glucose control but whether that is clinically significant is unclear (eg https://jamanetwork.com/journals/jama/fullarticle/2767160). Rather than an advertorial on TCMP, I’d like to see data from an unconflicted source citing improvements in outcomes that matter to patients, and economic analysis that helps us figure out for which patients these offer good value (they may be an excellent tool for some patients and not others).
The BC Health Technology Assessment Committee (of which I am now a part, but was not at the time of this work) did look at these technologies (https://www2.gov.bc.ca/gov/content/health/about-bc-s-health-care-system/partners/health-authorities/bc-health-technology-assessment/health-technology-assessments/glucose-monitoring) .
You will find a simple, unconflicted summary of the research so far (from an American perspective) here: https://www.aafp.org/afp/2020/0601/p646.html, an excerpt:
“No long-term studies have been performed to determine whether continuous glucose monitoring improves patient-oriented outcomes in type 2 diabetes. Compared with finger-stick monitoring, continuous glucose monitoring has not been shown to improve AlC levels after six months in patients receiving multiple daily insulin injections (7.7% vs. 8.0% in one study and 8.4% vs. 8.3% in another study).2,3 In a randomized study of 158 patients, there was no difference in overall or diabetes-specific quality of life at six months between patients using continuous glucose monitoring and those who were self-monitoring.3
The cost of continuous glucose monitoring ranges from $2,500 to $6,000 per year. A flash reading device costs approximately $100, with replaceable sensors costing another $120 to $200 monthly.5 Other devices cost $1,000 to $1,400, with replaceable sensors costing an additional $35 to $100 every seven to 10 days. Yearly battery replacement costs about $500.6 The cost-effectiveness of continuous glucose monitoring in patients with type 2 diabetes has not been studied. . . ”
For now, I would not change my practice based on the content of this post.
I’ve used one of these devices on my father, but I’m not convinced the price is worth it.
This article sums up some of the issues with these devices. https://www.statnews.com/2022/01/10/continuous-glucose-monitoring-diabetes-care/?utm_source=STAT+Newsletters&utm_campaign=848b8ea936-MR_COPY_01&utm_medium=email&utm_term=0_8cab1d7961-848b8ea936-150234785
Thank you this Gerri,
As someone with T1D for my 54th year I find the rtCGM extremely effective.
I started with Clinitest tablets in urine samples at 9 years of age and I think I am lucky to have made it through my teenage years at all. When I was in my mid twenties I purchased my first BGM but the test strips and even the monitor were expensive and would have been cost prohibitive without extended health coverage. Over the decades I found, with the analog insulin types, that I was testing up to 12 or 16 times to either watch my high blood sugars come down or anxiously watch the low BG come back up and stabilize while calculating duration of the last insulin injection.
An online calculator/spreadsheet to show the cost of rtCGM and isCGM versus how many test strips (often reluctantly done) are equal in cost or greater than that of either CGM type would be helpful.
I believe that the vast majority of diabetics of either T1D or T2D given a month long trial of a CGM would prefer it to a HBGM. There are unintended wasted test strips and often times where one must repeat test in a short period of time. I am biased towards CGMs for all who find them useful and find it presumptuous that someone may think they know what system I should have based on their assessment of necessity and of cost.
I have been using Loop (provided by BCD) for about 2 years and its ability to show predictive blood glucose is invaluable.
I understand “alarm fatigue” especially if your high glucose setting alarm is triggered as blood glucose is rising then the same high glucose reading is triggered again as BG is dropping below the trigger set point however I will live with it as opposed to a HBGM which is still necessary to double check unexpected CGM readings and to add a calibration if desired or as required to the CGM settings. I have experienced false low glucose readings when the sensor was compressed during sleep by sleeping on my side with a shoulder sensor placement but this can be handled by thoughtful placement of the sensor.
Thank you for sharing your insight and experience.
I have to agree with some of the comments above. As Jessica Otte remarked, I wonder whether the knowledge patients gain from these devices leads to better “patient-important” outcomes? Would the vast amount of data these devices provide help or hinder clinicians already burdened with too much information, and not enough time to processes it? I also worry that these technologies will exclude those of lower socioeconomic status (based on cost), a demographic most severely affected by type 2 diabetes. Finally, I have concerns that the ‘glucocentric’ approach to diabetes care that these technologies promote may detract from vital lifestyle changes that can prevent, control and even reverse type 2 diabetes, changes that may add other quality of life benefits!
It scan excellent article. I am of the opinion the device is for the difficult to control diabetics who are on insulin, especially the young and very active patients. There has to be a high degree of motivation and along with the ability to pay $80-100 per two weeks.
The overwhelming response from users, especially the parents of young, and anyone who is active is that these devices are “game-changers.” The following is not an exhaustive list:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5819241/;
https://www.liebertpub.com/doi/epdf/10.1089/dia.2021.0007;
https://asset-pdf.scinapse.io/prod/2898920858/2898920858.pdf;
https://www.liebertpub.com/doi/abs/10.1089/dia.2018.0199.
The motivation to use these devices is less than for using an HBGM, as there are no finger pokes; rtCGMs link via blue tooth technology in realtime with no further actions other than carrying a phone reader (and applying the device once every 10 to 14 days); and the person is notified via alarms with high/low readings; 24/7 data is obtained; there are several adhesives, easily obtained at a reasonable cost, for ostomies that can be used to keep these devices on the person; rtCGM is now included under the BC Fair Pharmacare formulary once special authority is arranged.
I believe that these devices should be offered full-time to anyone on insulin. Cost is a significant barrier, one we all have to address. In my practice, I often fill in compassionate care program requests, and the companies often do supply these devices free of charge. In many cases, insurance companies do cover the costs, although it is a significant issue for me to constantly have to fill in forms to prove need. But I believe that it is well worth my time and effort. Persons living with diabetes are able to tighten control, even if their A1C was under 7.0 (the suggested target for most with diabetes), more quickly and with less work (and worry).
These devices do provide a huge amount of information, which can be overwhelming. But there are succinct reports, with easily understood graphs, offering time above target, time in target, and time below target, along with estimated A1C and standard deviation. The time necessary to review reports is less than it takes to read this post.
Lower socioeconomic individuals with a low (or no) deductible are fully covered under Fair Pharmacare once special authority is obtained. Anyone on long-acting and mealtime insulin regardless of their diagnosis of type 1 or type 2 qualifies. If a device that is not covered under Fair Pharmacare is chosen, individuals with low income are often supplied sensors when an application is made for compassionate care. Lastly, there is a large amount of literature that suggests that treating high blood sugars must be done early. Over-reliance on lifestyle measures, which is often a real issue for low-income persons, especially those who are relying on food banks (which happens more often these days), condemns these folks to future complications. In my practice, the use of these devices shows persons wearing them the effects of their lifestyle actions. A walk may reduce their blood sugars (or not). Pasta usually results in high blood sugar. Persons wearing these devices can see their own actions in real-time (ie not just in the MD office or clinic). And the use of more intense management strategies does not mean those lifestyle strategies are not discussed, or that care is “glucocentric.” It simply means that all available tools are offered to persons living with diabetes to help them self-manage their condition.
Dr. Otte, the author of this piece did receive monies from Sanofi several years ago for educational lectures given to nurses on how to adjust insulin. As well, the author of this piece was the case manager in a study funded by Sanofi to determine if case management was an effective method to help patients. However, this was several years ago (completed in 2015), and she has not had funding from Sanofi since.
The monitor that is offered by Sanofi, the iBGstar, is a capillary blood glucose monitor. It does download to an iPhone or an iPad to be able to send the data to healthcare providers, but the iBGstar is not a CGM in any sense. The iBGstar uses a lancet, and strips, much like all of the home blood glucose monitors used for capillary monitors now available.
Dr. Otte, you state that “You will find a simple, unconflicted summary of the research so far (from an American perspective) here: https://www.aafp.org/afp/2020/0601/p646.html, …” This link is to a letter to the editor, which, by definition is an opinion. As weel, the editorial is from 2019, so the information is dated. Since that time, Diabetes Canada has released new guidelines which indicate rtCGM is essential for anyone on insulin regardless of the diagnosis of type 1 or 2.
Ian Mitchell, could I ask if your father is on a hypoglycemic medication, oral or injectable? As well, is your father elderly, and does he self-manage his diabetes (ie meds, exercise, diet)?
CGMs, either rt or is, are not toys. If persons living with diabetes don’t plan to make any changes or does not plan to look at the data, the devices are not helpful. But for persons who had no idea how certain exercises affect their blood sugars, these devices can be an eye-opener for both persons with diabetes as well as their caregivers. Resistant training exercises can increase blood sugars, as a CGM will show you. Not all carb foods are created equal, as a CGM will show you. And those who get a full night sleep may find that their blood sugars are more in control, as a CGM will show you. Yes, you could use blood capillary testing, but the number of finger pokes would be daunting, and painful.