The Relationship of Hemoglobin A1C to Time-in-Range in Patients with Diabetes

• Published in: Diabetes technology & therapeutics Vol. 21; no. 2; p. 81
• Main Authors: Vigersky, Robert A, McMahon, Chantal
• Format: Journal Article
• Language: English
• Published: United States 01.02.2019
• Subjects: Adolescent; Adult; Aged; Blood Glucose - analysis; Blood Glucose Self-Monitoring; Child; Diabetes Mellitus, Type 1 - blood; Diabetes Mellitus, Type 1 - drug therapy; Diabetes Mellitus, Type 2 - blood; Diabetes Mellitus, Type 2 - drug therapy; Female; Glycated Hemoglobin A - analysis; Humans; Hypoglycemic Agents - therapeutic use; Insulin - therapeutic use; Insulin Infusion Systems; Male; Middle Aged; Young Adult; Continuous glucose monitoring; HbA1C; Time-in-range
• ISSN: 1557-8593
• DOI: 10.1089/dia.2018.0310

There has been recent recognition of the limitations of hemoglobin A1C (HbA1C) in describing both short- and long-term glycemic control. Continuous glucose monitoring (CGM) provides robust data about short-term glycemic control and provides metrics such as percent time-in-range (%TIR) that are now routinely reported to describe the change in glycemic control after an intervention in a clinical study or a change in therapy in a patient's care. Recent studies have shown that %TIR may have similar associations with diabetes microvascular complications as does HbA1C. The relationship of %TIR to the long-standing metric of overall glycemic control has not been clearly defined to date. Articles that report paired HbA1C and %TIR metrics (n = 1137) or HbA1C and frequent self-monitoring of blood glucose (SMBG) (n = 1440) across a wide range of HbA1Cs, technologies, and subject demographics were reviewed to determine the correlation of these metrics. Selected paired HbA1C and %TIR data from 18 articles were evaluated by linear regression analysis and Pearson's correlation coefficient. There was an excellent correlation between the two (R = -0.84; R  = 0.71). This relationship did not change after excluding one study that used SMBG or six studies with ≤7 days of CGM. For every absolute 10% change in %TIR, there was a 0.8% (9 mmol/mol) change in HbA1C. There is a good correlation between HbA1C and %TIR that may permit the transition to %TIR as the preferred metric for determining the outcome of clinical studies, predicting of the risk of diabetes complications, and assessing of an individual patient's glycemic control.