Blood glucose monitoring devices

Key to this is working out what the person with diabetes wants, what features are important to them, and then having some understanding of the variety of glucose devices available, and being able to recommend the most appropriate device for that individual.

[Music] Welcome to the Australian Prescriber Podcast. Australian Prescriber, independent, peer-reviewed, and free.

Hi. Welcome to the Australian Prescriber Podcast. My name is Jo Cheah. I'm a hospital pharmacist in Melbourne, and your host for this episode. It's my pleasure to introduce Dr Benjamin Sly, an endocrinologist at the Princess Alexandra Hospital in Brisbane. Welcome, Ben.

Thanks for having me, Jo.

Ben and his co-author Janet Taylor have written about blood glucose monitoring devices in Australian Prescriber. Thanks again for coming on the program.

No problems.

So Ben, just to start off the interview today, why is blood glucose monitoring important for the management of diabetes, and who would you recommend blood glucose monitoring for?

Thanks, Jo. Blood glucose monitoring is useful for many people with diabetes, for a number of reasons. For the person with diabetes, it gives them a valuable insight into their glucose trends and can allow information and positive lifestyle adaptations to occur. Providing that data to their clinicians who are overseeing diabetes management can also guide clinician-recommended management.

Certainly in terms of glucose monitoring, it really is essential for people with diabetes who are using insulin or sulfonylureas to monitor their blood glucose levels. Not everyone with diabetes necessarily needs to monitor glucose levels, but people with diabetes who are pregnant or planning pregnancy, those who are undergoing dietary changes or changes to their physical activity, other medication changes, for instance if they're started on steroid therapy or antipsychotic therapy which may change their glucose levels. And then also in the setting of elective surgery, fitness to drive assessments and before performing other high-risk activities, this may be important. But really this needs to be individualised for the person and their clinical condition and discussed with their local practitioner.

And what are the differences between capillary blood glucose monitoring and continuous blood glucose monitoring?

So I imagine everyone is familiar with capillary or fingerprick blood glucose monitoring. This has been traditionally the method for self-monitoring of glucose which people with diabetes undertake. This would be performed using one of the many glucometers available in Australia, using the glucose strips, providing a fingerprick blood sample with the point-in-time blood glucose result displaying on the meter and saving within the device. And this is appropriate for most forms of diabetes.

Continuous glucose monitoring or interstitial glucose monitoring is something which is becoming more and more important in the diabetes landscape. Certainly people with type 1 diabetes can now access subsidised continuous glucose monitors. This measures an electrical current in the interstitial fluid and provides a correlated glucose level. It's important to recognise that this lags a few minutes behind the true capillary glucose level. The continuous glucose monitor’s very helpful in providing not just a point-in-time glucose level, which they do, but also lots of valuable longitudinal data and trending glucose data, which can help the practitioner make decisions about treatment or real-time decisions in terms of exercise and diet and insulin adjustments, for instance.

Continuous glucose monitoring can also be used for people with type 2 diabetes and in fact guidelines do recommend that it be offered to people with type 2 diabetes who are using insulin. Although in Australia there's no subsidy for this.

And in terms of the factors that you would consider when choosing a blood glucose monitor for a patient, do you mind going through some of those factors?

I think it's important to take into consideration what factors or what functionalities for their glucose monitoring device are most important to that person with diabetes. You can imagine that a person with diabetes who is vision impaired, if they are provided a very small glucose meter with a small display, it might make this difficult to check their glucose level in the appropriate manner.

So things that could be considered are firstly the size and the functionality of the device. The features that are available include whether the device is compatible with ketone testing, which might be important for someone with type 1 diabetes or even someone using an SGLT2 inhibitor with type 2 diabetes. If the device has functionality to sync their data with a paired smartphone application, that may be more important for some people, less important for others. The capacity to use the glucometer to provide recommendations regarding insulin dosing in terms of a bolus calculator is something which is very valuable for some people using insulin. And also the capacity to log insulin doses within the device or on the paired smartphone app may be very valuable in helping the person with diabetes and their clinician overseeing their care review their trends prior to the appointment and make appropriate adjustments.

So I think key to this is working out what the person with diabetes wants, what features are important to them, and then having some understanding of the variety of glucose devices available and being able to recommend the most appropriate device for that individual. I recognise that there are numerous models and it would be difficult for a general practitioner or community health practitioner who is not dealing with diabetes exclusively to be fully up to speed with all those options. So referring on to someone with more expertise in the diabetes field, such as a diabetes educator or pharmacist, could assist the person with diabetes in choosing the most appropriate meter. There's also a lot of resources available through the NDSS, the National Diabetes Services Scheme, Diabetes Australia or the local state, Queensland Diabetes for instance.

And just out of my own interest, would anything change if you're considering selecting a device for a child or other special patient populations?

So children with diabetes, certainly are a niche population with specific needs. Most children with diabetes will have type 1 diabetes and would be eligible for continuous glucose monitor sensors. However, they still also need to have access to a capillary blood glucose monitor for safety.

Can I just clarify that patients for example who are using continuous blood glucose monitoring, should they always have a capillary blood glucose monitor available as well?

Yes, absolutely. So the continuous glucose monitor is very valuable in providing real-time information to people with diabetes in terms of their absolute interstitial glucose value and the trend of whether they're up, flat or dropping glucose. However, we acknowledge that they're not 100% concordant and accurate, as opposed to a capillary glucose monitor, and particularly in the setting of extreme hypo- or hyperglycaemia.

So we would always recommend that someone using continuous glucose monitor have access to capillary glucose monitoring for confirmatory testing in situations where accuracy may be compromised. Of course there may be situations where there are connectivity issues with the continuous glucose monitor and having the capillary glucose monitor available for confirmatory testing is essential.

And you mentioned connectivity being one issue for example. Are there any other issues that might arise with using either capillary blood glucose monitors or continuous blood glucose monitors?

Just to carry on with the continuous glucose monitors, depending on whether they're paired with an insulin pump or not, if they are paired just with the phone and not an insulin pump, then you need access to your phone. Phone needs to be charged. And these continuous glucose monitors, the sensor component, or the whole combined sensor and transmitter component for some devices, they have a lifespan, so they will effectively expire and need to be replaced. So having access to the sensors, a new sensor at the time, would be important.

I think it’s important to acknowledge as well that there are factors which can affect accuracy of continuous glucose monitors and we’ve talked about rapidly changing glucose levels or extreme hypo- or hyperglycaemia. There are certain medications which can interfere with continuous glucose monitor results—hydroxyurea, paracetamol in high doses or intravenous vitamin C potentially interfere with continuous glucose monitor accuracy. For capillary glucose monitoring in addition to those medications, there are some others which may influence the accuracy.

And the accuracy of the devices needs to be considered in terms of the appropriate setting. So tests, storage, the environmental factors, so humidity or temperature or altitude. Physiological factors such as the hematocrit of the person testing their capillary glucose levels, triglyceride or bilirubin levels if they're significantly elevated can affect capillary glucose levels. And then human factors in terms of appropriate finger preparation, appropriate technique with performing the test.

So I think in all circumstances, it's important for someone with diabetes to recognise that, if they have a capillary glucose or a continuous glucose monitor recording that seems inaccurate and incongruent with what they would expect, to repeat the test, to consider calibration if indicated of either their capillary glucose monitoring device or their continuous glucose monitor device if appropriate, especially before making any treatment-related decisions.

And just for my knowledge as well, is continuous blood glucose monitoring an invasive type of procedure?

Yeah. So continuous interstitial glucose monitoring, we would classify it as invasive but it's very minimally invasive. The sensors are inserted using a device with a tiny monofilament which sits underneath the skin and an adhesive which secures the sensor in place. So it's very very rare that a person with diabetes using a continuous glucose monitor has an issue with pain at insertion. There is a small risk of infection at insertion sites and certainly assessment of CGM sites would be recommended when people with diabetes are seeing their health professional as part of their overall assessment.

Thank you Ben. And given all of the data that we can collect from both types of monitoring devices, what outcomes or indicators are you looking for to see if the selected monitoring, along with the patient's treatment regimen, is working well for your patient with diabetes?

I think this is something which is very important to establish between the clinician and the person with diabetes. I think if the person with diabetes understands what their treatment goals are, it helps them in between appointments to work towards achieving that and making changes in lifestyle which may allow them to achieve those goals. And the parameters would be different really for everyone. And this is where a discussion needs to determine what an individual goal may be.

So for a young person with type 1 diabetes, we would be using parameters such as their time in range, which is a CGM metric, which allows us to identify what proportion of every 24-hour period they spent between interstitial glucose of 4 and 10 mmol/L. And there are societal guidelines which suggest appropriate targets for that time in range. We would also consider how frequent or the time spent below target range.

Of course hypoglycaemia can be potentially dangerous and this is an important consideration when the clinician is seeing a person with diabetes—their hypoglycaemia burden. For someone undertaking capillary glucose monitoring, depending on their type of medications that they're using, they may not need to check their glucose levels at all if they're on a stable regimen of oral hypoglycaemic medications at target HbA1c levels. They may benefit from a morning capillary glucose check to ensure no hypoglycaemia and a fasting level within an appropriate range for that individual, which might be 5 to 7 mmol/L for one person. That might be 6 to 10 mmol/L for another person depending on their age, comorbidities etc. And postprandial glucose monitoring, so glucose levels 2 hours after meals, may be a useful indicator for other people in different situations.

I know you mentioned earlier in the episode that the continuous blood glucose monitors are subsidised for patients who have type 1 diabetes but not subsidised for patients with type 2 diabetes. Can you give some overall information about how patients access blood glucose monitors?

Yeah. So there are a number of different ways. I think generally the first port of call would be their community pharmacy, which is an NDSS access point. The community pharmacy can provide access to capillary glucose monitoring devices. And if people are signed up to the NDSS, National Diabetes Services Scheme, they can receive a rebate on any cost. They may be able to contact the company directly and be provided a glucose monitor. Or if seeing a diabetes professional such as a diabetes educator or a hospital service, they may be provided a glucometer as well. Capillary glucose monitors can actually be purchased within major supermarkets. However, it's worth acknowledging that not all capillary glucose testing strips are subsidised through the NDSS and it would be worthwhile confirming that the compatible strips are on the NDSS before purchasing a glucose monitor.

Certainly, again, contacting your state-based diabetes service such as Diabetes Queensland or contacting the NDSS, there's a lot of information available for people with diabetes.

For continuous glucose monitor use, people with type 1 diabetes need to be registered with the NDSS to access subsidised continuous glucose monitors. For certain groups such as those under 21, those with concessional status, those who are pregnant or planning pregnancy, or those who are Aboriginal or Torres Strait Islander, they can access continuous glucose monitor devices entirely free. For other people with type 1 diabetes who do not meet those criteria, there's a small monthly co-payment. But these devices are still largely subsidised.

A clinician has to complete the NDSS application for these people to receive the subsidy, but then they can be purchased through the website of the particular device or accessed through their NDSS care point such as a community pharmacy.

Lastly, is there anything that you would like to see change in this field of medicine or anything that you foresee in terms of research that you'd like to mention to the audience?

I would just like to highlight that the field is rapidly changing. In the past one to two years, we've had numerous versions of continuous glucose monitor devices and the linking with insulin pump software. So I think it's important for the person with diabetes who is using a continuous glucose monitor, especially one linked with an insulin pump, that they have ongoing connection with a diabetes health professional to ensure that they have access to the most-up-to date product, which may improve functionality for them.

I think for those using capillary glucose monitoring devices, again, there are constant updates in terms of availability of devices, connectivity with apps, and I think it's important as well that ongoing connection with health professionals to ensure that the most appropriate devices are being used for that person can really help them optimise their overall diabetes care.

And I'd also recommend to our listeners to have a look at the article that you and Janet have written. There are some comprehensive tables in there about features of different types of glucometers and as you said, it's really important for clinicians to stay up to date given the rapidly evolving diabetes medication field. That brings us to the end of the episode, Ben. Thank you so much for joining us today.

My pleasure. Thanks for having me, Jo.

[Music]

Dr Benjamin Sly's full article is available on the Australian Prescriber website. The views of the host and the guests on the podcast are their own and may not represent Australian Prescriber or Therapeutic Guidelines. I'm Jo Cheah, and thanks again for joining us on the Australian Prescriber Podcast.