SAT-126 The Relationship of Continuous Glucose Monitoring (CGM)-Derived Time-in-Range (TIR) to Hemoglobin A1c (HbA1c)

ENDO 2019 Abstract Background The limitations of glycated hemoglobin (HbA1c) in describing both short- and long-term glycemic control have been recognized recently. Continuous glucose monitoring (CGM) provides robust short-term glycemic control data and important metrics such as time-in-range (TIR), and the TIR of 70-180 mg/dL (3.9-10 mmol/L) is now accepted as the target for patients with diabetes. The change in daily percentage of TIR is used to describe glycemic control after an intervention in clinical trials and after a treatment modification in clinical practice. Recent studies have shown that TIR has a similar association with diabetes microvascular complications as does HbA1c (1,2). The relationship of TIR to the long-standing metric of overall glycemic control (HbA1c) has not been clearly defined to date. Methods Manuscripts and publications that reported paired HbA1c and CGM-derived TIR or HbA1c and frequent self-monitoring of blood glucose (SMBG) measurements across a wide range of HbA1c levels, technologies, and subject demographics were reviewed to determine the correlation of these metrics (1, 3-17). Results There was an excellent correlation between TIR and HbA1c (R(2)=0.71) where TIR = -12.9*HbA1c + 157. When the results derived from frequent SMBG performed in the DCCT study (1) were excluded, a similar correlation (R² = 0.71; TIR = -12.9*HbA1c + 157) was determined. A 10% change in TIR (e.g., between 50% and 60%) was equivalent to a 0.78% and 0.74% change in HbA1c, respectively. A TIR of 100% was equivalent to an HbA1c level of 4.4%. Conclusions There is a good correlation between HbA1c and TIR, which may support the transition to TIR as a preferred metric for determining the outcome of clinical studies, predicting the risk of diabetes complications, and assessing an individual patient’s glycemic control. References 1.Diabetes Care. 2018 Oct 23. pii: dc181444.doi:10.2337/dc18-1444. 2.Diabetes Care. 2018 Nov;41(11):2370-2376. 3.Diabetes Care. 2009 Aug;32(8):1378-83. 4.Diabetes Care. 2011 Apr;34(4):795-800. 5.JAMA. 2016 Oct 4;316(13):1407-1408. 6.N Engl J Med. 2008 Oct 2;359(14):1464-76. 7.Lancet Diabetes Endocrinol. 2016 Nov;4(11):893-902. 8.Lancet Diabetes Endocrinol. 2017 Sep;5(9):700-708. 9.JAMA. 2017 Jan 24;317(4):379-387. 10.Ann Intern Med. 2017 Sep 19;167(6):365-374. 11.JAMA. 2017 Jan 24;317(4):371-378. 12.PLoS One. 2018 Apr 13;13(4):e0194759. 13.Forlenza GP et al., Safety evaluation of the MiniMed™ 670G system in children 7-13 years of age with type 1 diabetes, unpublished. 14.Diabetes Metab Res Rev. 2018 Oct 21:e3092.doi:10.1002/dmrr.3092. 15.Diabetes Technol Ther. 2018 Nov;20(11):751-757. 16.Diabetes Technol Ther. 2018 Nov;20(11):715-724. 17.Diabetes Res Clin Pract. 2018 May;139:357-365.