title: Defining the relationship between average glucose and HbA1c in patients with type 2 diabetes and chronic kidney disease.
abstract: OBJECTIVE
  To examine the relationship between average glucose (AG) and HbA1c in patients with and without chronic kidney disease (CKD) and type 2 diabetes.
  
  
  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.
authors.affiliation: Monash Applied Research Stream, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia; Diabetes and Vascular Medicine Unit, Monash Health, Melbourne, Australia.
authors.forename: Clement
authors.initials: C
authors.lastname: Lo
authors.affiliation: Diabetes and Vascular Medicine Unit, Monash Health, Melbourne, Australia.
authors.forename: Michelle
authors.initials: M
authors.lastname: Lui
authors.affiliation: Monash Applied Research Stream, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia.
authors.forename: Sanjeeva
authors.initials: S
authors.lastname: Ranasinha
authors.affiliation: Monash Applied Research Stream, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia; Diabetes and Vascular Medicine Unit, Monash Health, Melbourne, Australia.
authors.forename: Helena J
authors.initials: HJ
authors.lastname: Teede
authors.affiliation: Department of Nephrology, Monash Medical Centre and Monash University, Clayton, Australia.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Kerr
authors.affiliation: Department of Nephrology, Monash Medical Centre and Monash University, Clayton, Australia.
authors.forename: Kevan R
authors.initials: KR
authors.lastname: Polkinghorne
authors.affiliation: Diabetes Centre, Massachusetts General Hospital, Boston, USA; Harvard Medical School, Boston, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Nathan
authors.affiliation: Biostatistics Centre, Massachusetts General Hospital, Boston, USA; Harvard Medical School, Boston, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Zheng
authors.affiliation: Monash Applied Research Stream, School of Public Health and Preventive Medicine, Monash University, Melbourne, Australia; Diabetes and Vascular Medicine Unit, Monash Health, Melbourne, Australia; The George Institute for Global Health, Sydney, Australia. Electronic address: sophia.zoungas@monash.edu.
authors.forename: Sophia
authors.initials: S
authors.lastname: Zoungas
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism*; D015190:Blood Glucose Self-Monitoring / Q000379:methods*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000150:complications; D005260:Female; D005500:Follow-Up Studies; D006442:Glycated Hemoglobin / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000150:complications; D055815:Young Adult
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; D006442:Glycated Hemoglobin; C517652:hemoglobin A1c protein, human
keywords: Chronic kidney disease; Diabetes mellitus; Erythropoietin stimulating agent; Glycated haemoglobin