Continuous Glucose Monitoring and Glycemic Control in Patients With Type 2 Diabetes Mellitus and CKD

Abstract

Rationale & Objective: The accuracy of glycated hemoglobin (HbA1c) level for assessment of glycemic control in patients with chronic kidney disease (CKD) is uncertain. This study assessed the accuracy of HbA1c level using continuous glucose monitoring. Study Design: Diagnostic test study of HbA1c and serum fructosamine. The continuous glucose monitor was worn for 14 days. Glucose was measured every 15 minutes (up to 1,344 measurements). Average glucose concentration was calculated for each patient from the patient’s continuous glucose monitor measurements. Linear regression was applied to estimate the relationship between average glucose concentration and HbA1c and serum fructosamine levels. The influence of patient characteristics on the relationship between HbA1c and average glucose concentrations was examined in a multivariate regression model. Setting & Participants: Patients with type 2 diabetes and CKD (estimated glomerular filtration rate, 7-45 mL/min, not receiving dialysis) seen in an academic nephrology clinic. Tests Analyzed: The accuracy of HbA1c level for assessment of chronic glycemia. A secondary objective was to study serum fructosamine levels. Outcomes: The degree of correlation between continuous glucose monitoring–derived average glucose concentration and HbA1c level; serum fructosamine level was studied as a secondary outcome. Results: 80 patients wore the continuous glucose monitor for a mean of 12.7 ± 2.9 days. Average glucose concentration of all patients was 151.5 ± 55.7 mg/dL. Mean HbA1c level was 7.2% ± 1.5%. HbA1c level was highly correlated with average glucose concentration, described by the equation: average glucose concentration = 30.48 × HbA1c − 68.48; r = 0.82; P < 0.001. Serum fructosamine level was also significantly correlated with average glucose concentration; r = 0.55; P < 0.001. The strong correlation between average glucose concentration and HbA1c level was not affected by the severity of CKD, whereas the performance of serum fructosamine level, in contrast, degraded among patients with more severe CKD. Limitations: Relatively small sample size. Conclusions: HbA1c is an accurate measure of glycemic status among patients with CKD and type 2 diabetes. This relationship appears to hold true among patients with more severe CKD. Index Words: Type 2 diabetes, chronic kidney disease, continuous glucose monitoring, HbA1c, glycated hemoglobin, diagnostic test study