Diabetes is one of the most common lifelong chronic diseases in human beings. Doctor attempt to quantify glucose in the urine date back to the mid-1800s. While the first glucose meter was used in the 1970s with the Dextrostix, but its precision and accuracy were poor.  By 1980, the Dextrometer was launched; this meter used the Dextrostix along with a digital display. During the 1980s, meters and strips requiring less blood became available, all at a cheaper price (1). This allow self-monitoring of blood glucose (SMBG) at a specific point in time for diabetes patient. 

Non-invasive blood glucose allows continuous Glucose Monitoring (CGM) technology has become an international research topic and a new method which could bring relief to a vast number of patients. It can provide continuous real-time measurement of glucose levels, alerts for hypoglycemia and hyperglycemia, and a detailed assessment of glycemic variability (2)

Non invasive glucose monitoring products were classified into three categories: (1) Noninvasive optical glucose monitor (NIO-GM),(2) Noninvasive fluid sampling glucose monitor (NIFS-GM), and (4) Minimally invasive glucose monitor (MI-GM). These technologies are generally characterized as providing continuous or intermittent glucose measurements with minimal or no pain. (3) NIO-GM involves sending harmless, low-energy radiation through a vascular body site and extracting information about the glucose concentration from the collected signal. NIFS-GM products center on technologies capable of collecting and analyzing samples of ISF, tears, sweat, or saliva. The majority of MI-GM products currently on the market are devices that require the user to insert the sensing element in the subcutaneous space.

Advantage of CGM over conventional self-monitoring has been reported by a number of clinical trials for improved HbA1c levels, decreased time in hypoglycemic /hyperglycemic ranges, and reduction of hypoglycemic events in people with type 1 diabetes (5-7).Beside the clinical aspect, the patient was also shown to have beneficial aspect psychologically. (8) CGM provides a better idea on the glucose trend. When combined with the use of insulin pump, the algorithm helps to predict low blood glucose, thereby suspending insulin infusion on or before low blood glucose. This helps to reduce hypoglycaemia, especially at night time.

Limitation

Individual differences (including age, skin color, skin condition, etc.) will cause large errors to the measurement results, resulting in the consistency, stability and reliability of the instrument not being strongly proven (3) Integrating CGM into clinical practice can be challenging for several reasons. Common issues reported include data overload, increased clinic staff time, and the need for HCP education on data interpretation (9) Although the interstitial fluid glucose levels in CGM usually correlate with blood glucose levels, there is a time lag between the two. This will result in a discrepancy between the CGM glucose and blood glucose values, especially when the blood glucose rises or drops very quickly. most healthcare providers suggest the patients check blood glucose when CGM glucose levels are too low or too high, before they decide on any intervention.

Conclusion

CGM has shown impressive scientific, technological, engineering, and clinical advances, providing benefits to many people with diabetes. We will expect more and more utilization of CGM in the future and hence improving both patient outcomes. As advances in technology and clinical evaluation continue, one hopes and expects that increased popularity will generate economies of scale, drive further cost reductions, and further improvement of usability, sparking the interest of patients and healthcare providers, and further stimulating usage.(10)

Reference 

1. Role of Continuous Glucose Monitoring in Diabetes Treatment. https://www.ncbi.nlm.nih.gov/books/NBK538968/

2. Oliver Schnell, Katharine Barnard, Richard Bergenstal Role of Continuous Glucose Monitoring in Clinical Trials: Recommendations on Reporting Diabetes Technol Ther . 2017 Jul;19(7):391-399

3. Trisha Shang, Jennifer Y. Zhang, Andreas Thomas Products for Monitoring Glucose Levels in the Human Body With Noninvasive Optical, Noninvasive Fluid Sampling, or Minimally Invasive Technologies J Diabetes Sci Technol. 2022 Jan;16(1):168-214.

4. Liu Tang Shwu Jen Chang Ching-Jung Chen et al *Non-Invasive Blood Glucose Monitoring Technology: A Review Sensors (Basel). 2020 Dec; 20(23): 6925.

5. Lang J, Jangam S, Dunn T, Hayter G. Expanded real-world use confirms strong association between frequency of flash glucose monitoring and glucose control [Abstract ATTD19-0299]. Diabetes Technol Ther 2019;21(Suppl. 1):A40

6. Battelino T, Phillip M, Bratina N, et al.: Effect of continuous glucose monitoring on hypoglycemia in type 1 diabetes. Diabetes Care 2011;34:795–800

7. Beck RW, Hirsch IB, Laffel L, et al.: The effect of continuous glucose monitoring in well-controlled type 1 diabetes. Diabetes Care 2009;32:1378–1383

8. Kubiak T, Mann CG, Barnard KC, Heinemann L: Psychosocial aspects of continuous glucose monitoring: connecting to the patients' experience. J Diabetes Sci Technol 2016;10:859–863

9. Rodbard D. Continuous glucose monitoring: a review of successes, challenges, and opportunities. Diabetes Technol Ther 2016;18(Suppl. 2):S3–S13

10. David Rodbard, MD Continuous Glucose Monitoring: A Review of Successes, Challenges, and Opportunities Diabetes Technol Ther. 2016 Feb 1; 18(Suppl 2): S2-3–S2-13.