Associations between HbA1c 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.