Continuous glucose monitoring in diabetes, what do we ask for in 2021?

Rosa Corcoy i Pla

Director of the Diabetes Unit,

Department of Endocrinology and Nutrition,

Hospital de la Santa Creu i Sant Pau, Barcelona

Universitat Autònoma de Barcelona

CIBER-BBN

Diabetes is an undeniable global health problem, no matter how you look at it. As an example, you can take a look at the data provided by the International Diabetes Federation at https://www.diabetesatlas.org/. Some figures related to the number of affected individuals: more than one million children have type 1 diabetes, 1 in every 11 adults has type 2 diabetes, the number of adults living with diabetes has tripled in 20 years, and almost 16% of pregnancies are affected by some type of diabetes.

Data on its consequences: in most countries, diabetes is the leading cause of blindness in the working-age population; it is one of the main causes of kidney disease requiring dialysis or transplantation; it reduces life expectancy especially in women and when diagnosed at a young age; episodes of hypoglycemia are frequent in patients treated with insulin or sulfonylureas, affecting quality of life, limiting glycemic control, and having short- and long-term consequences. In pregnancy, it increases the risk of many complications for both the mother and the child, including malformations, preeclampsia, or premature birth. The latest complication to add to the list is a worse outcome in case of infection by SARS-COV2.

“More than one million children have type 1 diabetes, 1 in every 11 adults has type 2 diabetes, the number of adults living with diabetes has tripled in 20 years, and almost 16% of pregnancies are affected by some type of diabetes”

With this scenario, strategies to reduce its impact involve both prevention and improvement of its treatment. The latter includes modifications in lifestyle, medications, and monitoring. Precisely, one of the functions of the beta cells of the pancreas is to measure the amount of glucose in the blood and adjust the insulin it secretes accordingly. This monitoring function is what we will have to replace in order not to “drive” treatment blindly, especially if it includes insulin or medications that can cause hypoglycemia. Since blood glucose is the key parameter to know, glucose concentration in other body fluids has also been addressed because it reflects that of the blood, although with many differences depending on the sample. Thus, it has been tested in urine, saliva, tears, sweat, or subcutaneous tissue.

Years ago, measuring glucose in urine was the usual monitoring method and subcutaneous tissue is where glucose sensors are inserted, whose use is currently exponentially increasing. Although the information provided by glucose sensors is less accurate than when measured directly in blood and with a few minutes delay, subcutaneous sensors have allowed continuous information on glucose evolution, which we know as continuous glucose monitoring (CGM). This CGM is currently the gold standard for patients with type 1 diabetes, in whom it has shown benefits in terms of quality of life, overall glycemic control, reduction of hypoglycemia episodes, and pregnancy complications. Since the introduction of commercially available systems in the early years of this century, CGM has evolved to real-time, included alarms for high and low values, progressed in accuracy, and data transmission capacity. Thus, a patient’s glucose information can be transmitted over short distances, “communicating” with insulin pumps to increase or decrease the dose according to the results (“artificial pancreas”) or over longer distances allowing remote visualization by caregivers or healthcare professionals.

In the current pandemic situation, we have discovered new uses for these transmission applications, for example, facilitating non-presential visits by patients and also in some patients hospitalized for coronavirus, where transmitting glucose data to the nursing station bypasses the need for entry into the room solely for glucose measurement with all that entails (consumption of time and protective equipment as well as the possibility of contagion).

“Transmitting glucose data to the nursing station bypasses the need for entry into the room solely for glucose measurement with all that entails: consumption of time and protective equipment as well as the possibility of contagion”

As of today, what do we ask of CGM? That it improves accuracy and precision so that decisions based on its readings are more accurate, that information transmission is as user-friendly as possible and includes all the devices used by patients, that it is as non-invasive as possible, discreet, and that prices are affordable so that its use can be extended without price being a limitation.