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Diabetes The Rationale for Continuous Glucose Monitoring-based Diabetes Treatment Decisions and Non-adjunctive Continuous Glucose Monitoring Use David Price and Tomas Walker Dexcom, Inc., San Diego, California, US Abstract Self-monitoring of blood glucose (SMBG) is now recognised as a core component of diabetes self-management. However, there are many limitations to SMBG use in individuals with diabetes who are treated with intensive insulin regimens. Many individuals do not test at the recommended frequencies. Additionally, because SMBG only provides a blood glucose reading at a single point in time, hypoglycaemia and hyperglycaemia can easily go undetected, limiting the user’s ability to take corrective action. Inaccuracies due to user error, environmental factors and weaknesses in SMBG system integrity further limit the utility of SMBG. Real-time continuous glucose monitoring (CGM) displays the current glucose, direction and velocity of glucose change and provides programmable alarms. This trending information and ‘around- the-clock’ vigilance provides a significant safety advantage relative to SMBG. No published clinical studies have evaluated outcomes when CGM is used as a replacement for SMBG; however, recent in silico studies support this indication. This article reviews the limitations of SMBG and discusses recent evidence that supports CGM-based decisions as an effective approach to managing insulin-treated diabetes. Keywords Continuous glucose monitoring (CGM), self-monitoring of blood glucose (SMBG), glucose monitoring, continuous subcutaneous insulin infusion (CSII), multiple-dose insulin (MDI), rate of change, glucose trend Disclosure: David Price and Tomas Walker are employees of Dexcom, Inc. Open Access: This article is published under the Creative Commons Attribution Noncommercial License, which permits any non-commercial use, distribution, adaptation and reproduction provided the original author(s) and source are given appropriate credit. Received: 22 January 2016 Accepted: 10 February 2016 Citation: European Endocrinology, 2016;12(1):24–30 Correspondence: David Price, Dexcom, Inc., 6340 Sequence Drive, San Diego, CA 92121, US. E: Support: The development of this manuscript was funded by Dexcom, Inc. Type 1 diabetes (T1D) and advanced type 2 diabetes (T2D) require intensive insulin therapy in combination with frequent glucose monitoring to optimise glycaemic control. Although the value of achieving normoglycaemia has been well demonstrated, 1 many individuals with insulin-treated diabetes are unable to meet established glycaemic targets without excessive and/or severe hypoglycaemia. 2–5 The introduction of self-monitoring of blood glucose (SMBG) devices in the late 1970s provided a tool for assessing current glucose levels, to calculate insulin dosages and inform decisions. When first introduced, SMBG met with scepticism, as some clinicians doubted the accuracy of the devices and that patients would know how to appropriately respond to the blood glucose data. Studies soon demonstrated the utility of SMBG in limited populations 6,7 and in 1993 the benefit of SMBG- based intensive diabetes management was validated in the Diabetes Control and Complication Trial. 1 SMBG is now recognised as a core component of diabetes self- management. 8–11 However, given recent advances in the accuracy, reliability and usability of continuous glucose monitoring (CGM), accurate CGM systems may now be capable of replacing SMBG as a primary source of glucose information. The purpose of this report is to review the limitations of SMBG and discuss recent evidence that 24 supports CGM-based decisions as an effective approach to managing insulin-treated diabetes. 12,13 Limitations of Self-Monitoring of Blood Glucose-based Decisions The American Diabetes Association (ADA) recommends that patients on intensive insulin regimens, multiple-dose insulin (MDI) or continuous subcutaneous insulin infusion (CSII) should consider SMBG prior to meals and snacks, occasionally following meals, at bedtime, prior to exercise, when low glucose is suspected, after treating low glucose and prior to critical tasks such as driving. For many patients, this will require testing six to 10 (or more) times daily. 14 Other organisations provide similar recommendations. 10,11 Many individuals do not test at the recommended frequencies. A recent survey of 16,061 participants in the T1D Exchange registry reported that 34% (n=3,630) performed SMBG zero to three times daily, 3 supporting an earlier survey that found SMBG non-adherence to be as high as 60%. 15 There are many reasons for non-adherence, including the pain and ‘hassle’ of testing and the perceived limited utility of the results. 16 The numerous steps required to perform a blood glucose measurement, contributing to the hassle factor, are shown in Table 1. TOU C H ME D ICA L ME D IA