Associations between HbA(1c) and continuous glucose monitoring‐derived glycaemic variables

AIMS: To identify clinically useful associations between HbA(1c) levels and various continuous glucose monitoring‐derived metrics. METHODS: We retrospectively analysed end‐of‐study HbA(1c) levels and >2 weeks of continuous glucose monitoring data collected from 530 adults with Type 1 diabetes or insulin‐requiring Type 2 diabetes during four randomized trials. Each trial lasted ≥24 weeks and provided central laboratory end‐of‐study HbA(1c) levels and continuous glucose monitoring data from the preceding 3 months. Participants were assigned to groups based on either HbA(1c) levels or continuous glucose monitoring‐derived glucose values. RESULTS: HbA(1c) was strongly correlated with mean glucose value (r=0.80), time spent with glucose values in the 3.9–10.0 mmol/l range (time in range; r=–0.75) and percentage of glucose values >13.9 mmol/l (r=0.72), but was weakly correlated with the percentage of glucose values <3.9 mmol/l (r=–0.39) or <3.0 mmol/l (r=–0.21). The median percentage of glucose values <3.0 mmol/l was <1.2% (<20 min/day) for all HbA(1c)‐based groups, but the median percentage of values >13.9 mmol/l varied from 2.5% (0.6 h/day) to 27.8% (6.7 h/day) in the lowest and highest HbA(1c) groups, respectively. More than 90% of participants with either <2% of glucose values >13.9 mmol/l, mean glucose <7.8 mmol/l, or time in range >80% had HbA(1c) levels ≤53 mmol/mol (≤7.0%). For participants with HbA(1c) ≥64 mmol/mol (≥8.0%), the median time in range was 44%, with 90% of participants having a time in range of <59%. CONCLUSIONS: The associations shown in the present study suggest that continuous glucose monitoring‐derived metrics may help guide diabetes therapy intensification efforts in an HbA(1c)‐independent manner.