Defining the relationship between average glucose and HbA1c in patients with type 2 diabetes and chronic kidney disease

• Published in: Diabetes research and clinical practice 2014-04, Vol.104 (1), p.84-91
• Main Authors: Lo, Clement, Lui, Michelle, Ranasinha, Sanjeeva, Teede, Helena J, Kerr, Peter G, Polkinghorne, Kevan R, Nathan, David M, Zheng, Hui, Zoungas, Sophia
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Biomarkers - blood; Blood Glucose - metabolism; Blood Glucose Self-Monitoring - methods; Chronic kidney disease; Diabetes mellitus; Diabetes Mellitus, Type 2 - blood; Diabetes Mellitus, Type 2 - complications; Endocrinology & Metabolism; Erythropoietin stimulating agent; Female; Follow-Up Studies; Glycated haemoglobin; Glycated Hemoglobin A - metabolism; Humans; Male; Middle Aged; Prospective Studies; Renal Insufficiency, Chronic - blood; Renal Insufficiency, Chronic - complications; Young Adult
• ISSN: 0168-8227; 1872-8227
• DOI: 10.1016/j.diabres.2014.01.020

Abstract Aims To examine the relationship between average glucose (AG) and HbA1c in patients with and without chronic kidney disease (CKD) and type 2 diabetes. Materials and methods 43 patients with diabetes and CKD (stages 3–5) with stable glycaemic control, and glucose-lowering and erythropoiesis stimulating agent (ESA) doses, were prospectively studied for 3 months and compared to 104 age-matched controls with diabetes, without CKD from the ADAG study. Over 3 months, AG was calculated from 7 to 8 point self-monitored blood glucose measurements (SMBG) and from continuous glucose monitoring (CGMS), and mean HbA1c was calculated from 4 measurements. AG and HbA1c relationships were determined using multivariable linear regression analyses. Results The CKD and non-CKD groups were well matched for age and gender. Mean AG tended to be higher ( p = 0.08) but HbA1c levels were similar ( p = 0.68) in the CKD compared with non-CKD groups. A linear relationship between AG and HbA1c was observed irrespective of the presence and stage of CKD. The relationship was weaker in patients with stage 4–5 CKD (non-CKD R2 = 0.75, stage 3 CKD R2 = 0.79 and stage 4–5 CKD R2 = 0.34, all p < 0.01). The inclusion of ESA use in the model rendered the effect of CKD stage insignificant ( R2 = 0.67, p < 0.01). Conclusions In patients with type 2 diabetes and CKD there is a linear relationship between HbA1c and AG that is attenuated by ESA use, suggesting that ESA results in a systematic underestimation of AG derived from HbA1c.