HbA1c, CGM data significantly differed in patients with kidney disease

Patients with diabetes and chronic kidney disease often had discordance between their HbA1c levels and continuous glucose monitoring (CGM) data, with the HbA1c being significantly higher on average than the CGM-calculated glucose, a French study found.

An observational study found discordance between HbA1c levels and continuous glucose monitoring (CGM) data in individuals with diabetes and chronic kidney disease (CKD).

A total of 355 CGM users (59% male) with diabetes (73% type 1, 20% type 2, 7% other) seen at three diabetes care centers in France from January 2019 to June 2021 were eligible for the study. Researchers compared those with diabetes and CKD (n=170) and those with diabetes but not CKD (n=185). All participants used the same intermittently scanned CGM device, and the researchers compared 14-day and 90-day glucose data to calculate the glucose management indicator and its discordance with lab-measured HbA1c level. Results were published April 25 by the Journal of Diabetes Science and Technology.

Patients in the CKD group were older (69.6 vs. 54.0 years; P<0.001), had a higher body mass index (29.0 vs. 27.6 kg/m2; P=0.038), and more frequently had type 2 diabetes than those in the group without CKD. The mean duration of CKD was 8.2 years, and the etiology of renal disease was diabetic nephropathy in 71.2% of cases. HbA1c level was significantly higher in the CKD group (8.2% vs. 7.9%; P<0.001), and discordance between HbA1c and the glucose management indicator derived from CGM was significantly higher in the CKD group than in the group without CKD (0.78% vs. 0.59%; P<0.005). An absolute difference greater than 0.5% was found in 68.2% of individuals with CKD versus 42.2% of those without CKD. Discordance was typically in favor of an HbA1c level higher than the glucose management indicator value, “which can lead to errors in changes in glucose-lowering therapy, especially for individuals with CKD,” the study authors wrote. “This latter population should benefit from the CGM to measure their glucose exposure more precisely.” They also suggested a specific new formula to calculate the glucose management indicator in the CKD group based on the linear regression between HbA1c and CGM mean glucose at 90 days: 3.558 + 0.026 × [90-day CGM mean glucose (mg/dL)] (r2=0.59).

The main limitation of the analysis is the lack of knowledge about the accuracy of intermittently scanned CGM in the CKD population, since there was no calibration of the CGM device worn, the authors said.

They added that while the physiological consequences of the discrepancy found in the study are unclear, future research should explore the difference in HbA1c and the glucose management indicator. The authors noted that a relationship between the glycation gap and the development of micro- or macrovascular complications has been hypothesized but said that a large prospective study is needed to validate this hypothesis.