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 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.