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Time for Change – Measuring blood glucose using HbA1c vs. Time in Range

by Trisha Thacker and Gabriela Ratzker of Advisor Squad team.

 

The most popular standardized measure of blood glucose levels used by people with diabetes is the Hemoglobin A1c Test. This test measures how much sugar is bound to the hemoglobin in the red blood cells and is thus also called the Glycohemoglobin Test. Since the red blood cells have an average lifespan of three months, the test reveals average blood glucose levels for three months. However, there are other factors that influence the HbA1C result such as cholesterol levels, kidney or liver disease, vitamin supplements and other conditions affecting hemoglobin such as anemia.

Moreover, since the test is an average of 3 months – it does not reveal the exact fluctuations in blood glucose that could have led to hyperglycemia and hypoglycemia. A person with extreme fluctuations in both directions may have the same HbA1c result as a person with a steady and stable blood glucose value. Additionally, the greatest drawback of HbA1c is that it doesn’t capture hypoglycemia, even though severely low blood sugar could be fatal.[1]

According to Dr. Tadej Battelino, the Head of Department of Pediatric and Adolescent Endocrinology at UMC Ljubljana, Slovenia, after several years of using HbA1c, it has become apparent that this measure doesn’t accurately represent the mean glucose levels for people with diabetes. This was first revealed by the 2008 study by Nathan DM[2] published in Diabetes Care. The study “sought to define the mathematical relationship between A1C and average glucose (AG) levels”[3] and showed that the HbA1c levels may not be appropriate for developing personal recommendations.

Thus, there is a need for more sophisticated and accurate measures of glucose level. The 2017 International Consensus on the Use of Continuous Glucose Monitoring (CGM) convened an international panel of experts to address this issue.[4] They suggested several key metrics such as glucose variability, glycemic variability and most importantly, time in range.

Time in Range (TIR) readings can be defined as the time period during which glucose values within a particular acceptable range. Although the limits can be individualized, they are typically set as between 70-180mg/dl.[5] According to the 2017 International Consensus on the use of CGM, the TIR data provides individuals with information about the amount of time they experience clinically significant hypo or hyperglycemia. Additionally, the paper recognizes that TIR is not a comprehensive measure and there is a need to quantify the time spent below and above a target range and to create severity thresholds. An example it provides, is dividing hyper and hypoglycemia as level 1 (monitor and act) and level 2 (immediate action), to allow more appropriate clinical response.[6]

Dr. Battelino was a co-author of the 2019 International Consensus on ‘Clinical Targets for CGM Data Interpretation,’ which developed recommendations on time in range.[7] He has also authored and co-authored over 200 manuscripts in international peer reviewed journals.

We had the pleasure to host Dr. Battelino as part of our Advisor Academy. When we asked him to comment on how Time in Range should be implemented as part of routine care he replied: “Targets for Time in range, recently agreed upon in a broad international consensus, are welcomed by health care professionals and people with diabetes. The concept of Time in range is derived from the daily routine of individuals with diabetes and therefore easy to understand and adopt as a treatment target. To maximize the time in the target range, both health care professionals and individuals with diabetes need artificial intelligence support for facilitating and accelerating the decision process. Closed-loop insulin delivery systems and computerized dose advisers can provide such assistance. Additionally, health care providers in diabetes need universal platforms for downloading different devices, for unifying the continuous glucose and therapy data analysis, and for data presentation. Professional dose adviser algorithms are of particular importance and when embedded into the universal data-download platforms instantly provide comprehensive data analysis and individualized dosing recommendations. The novel “digital clinic” environment thus help the health care providers and individuals with diabetes to spend less time on tedious data processing and more on things that really matter.”

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[1] https://diatribe.org/BeyondA1c

[2] https://www.ncbi.nlm.nih.gov/pubmed/18540046

[3] https://www.ncbi.nlm.nih.gov/pubmed/18540046 (ibid)

[4] https://care.diabetesjournals.org/content/40/12/1631

[5] https://diatribe.org/time-range-whats-achievable-goal-diabetes

[6] https://care.diabetesjournals.org/content/40/12/1631

[7] https://care.diabetesjournals.org/content/early/2019/06/07/dci19-0028

 

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