title: The Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation does not improve the underestimation of Glomerular Filtration Rate (GFR) in people with diabetes and preserved renal function.
abstract: BACKGROUND
  Our hypothesis was that both the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) and Modification of Diet in Renal Disease (MDRD) equations would underestimate directly measured GFR (mGFR) to a similar extent in people with diabetes and preserved renal function.
  
  
  METHODS
  In a cross-sectional study, bias (eGFR - mGFR) was compared for the CKD-EPI and MDRD equations, after stratification for mGFR levels. We also examined the ability of the CKD-EPI compared with the MDRD equation to correctly classify subjects to various CKD stages. In a longitudinal study of subjects with an early decline in GFR i.e., initial mGFR > 60 ml/min/1.73 m(2) and rate of decline in GFR (ΔmGFR) > 3.3 ml/min/1.73 m(2) per year, ΔmGFR (based on initial and final values) was compared with ΔeGFR by the CKD-EPI and MDRD equations over a mean of 9 years.
  
  
  RESULTS
  In the cross-sectional study, mGFR for the whole group was 80 ± 2.2 ml/min/1.73 m(2) (n = 199, 75 % type 2 diabetes). For subjects with mGFR >90 ml/min/1.73 m(2) (mGFR: 112 ± 2.0, n = 76), both equations significantly underestimated mGFR to a similar extent: bias for CKD-EPI: -12 ± 1.4 ml/min/1.73 m(2) (p < 0.001) and for MDRD: -11 ± 2.1 ml/min/1.73 m(2) (p < 0.001). Using the CKD-EPI compared with the MDRD equation did not improve the number of subjects that were correctly classified to a CKD-stage. No biochemical or clinical patient characteristics were identified to account for the under estimation of mGFR values in the normal to high range by the CKD-EPI equation. In the longitudinal study (n = 30, 66 % type 1 diabetes), initial and final mGFR values were 102.8 ± 6 and 54.6 ± 6.0 ml/min/1.73 m(2), respectively. Mean ΔGFR (ml/min/1.73 m(2) per year) was 6.0 by mGFR compared with only 3.0 by MDRD and 3.2 by CKD-EPI (both p < 0.05 vs mGFR) CONCLUSIONS: Both the CKD-EPI and MDRD equations underestimate reference GFR values > 90 ml/min/1.73 m(2) as well as an early decline in GFR to a similar extent in people with diabetes. There is scope to improve methods for estimating an early decline in GFR.
authors.affiliation: Department of Endocrinology and Diabetes, St Vincent's Hospital Melbourne, 4th Floor, Daly Wing, 35 Victoria Parade, PO Box 2900, Fitzroy, VIC, 3065, Australia. r.macisaac@unimelb.edu.au.|Department of Medicine, St Vincent's Hospital, University of Melbourne, Fitzroy, 3065, Victoria, Australia. r.macisaac@unimelb.edu.au.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: MacIsaac
authors.affiliation: Endocrine Centre, Austin Health, West Heidelberg, 3081, Victoria, Australia. elif.ekinci@unimelb.edu.au.|Menzies School of Health Research, Casuarina, 0811, Northern Territory, Australia. elif.ekinci@unimelb.edu.au.|Department of Medicine, Austin Health, University of Melbourne, Heidelberg, 3084, Victoria, Australia. elif.ekinci@unimelb.edu.au.
authors.forename: Elif I
authors.initials: EI
authors.lastname: Ekinci
authors.affiliation: Endocrine Centre, Austin Health, West Heidelberg, 3081, Victoria, Australia. erosha.premaratne@gmail.com.
authors.forename: Erosha
authors.initials: E
authors.lastname: Premaratne
authors.affiliation: Melbourne Pathology, Collingwood, 3066, Victoria, Australia. Zhong.Lu@mps.com.au.
authors.forename: Zhong X
authors.initials: ZX
authors.lastname: Lu
authors.affiliation: Endocrine Centre, Austin Health, West Heidelberg, 3081, Victoria, Australia. jmseah@gmail.com.
authors.forename: Jas-Mine
authors.initials: JM
authors.lastname: Seah
authors.affiliation: Department of Endocrinology and Diabetes, St Vincent's Hospital Melbourne, 4th Floor, Daly Wing, 35 Victoria Parade, PO Box 2900, Fitzroy, VIC, 3065, Australia. Yue.Lii@svha.org.au.|Department of Medicine, St Vincent's Hospital, University of Melbourne, Fitzroy, 3065, Victoria, Australia. Yue.Lii@svha.org.au.
authors.forename: Yue
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Endocrinology and Diabetes, St Vincent's Hospital Melbourne, 4th Floor, Daly Wing, 35 Victoria Parade, PO Box 2900, Fitzroy, VIC, 3065, Australia. drrayboston@yahoo.com.|Department of Medicine, St Vincent's Hospital, University of Melbourne, Fitzroy, 3065, Victoria, Australia. drrayboston@yahoo.com.
authors.forename: Ray
authors.initials: R
authors.lastname: Boston
authors.affiliation: Department of Endocrinology and Diabetes, St Vincent's Hospital Melbourne, 4th Floor, Daly Wing, 35 Victoria Parade, PO Box 2900, Fitzroy, VIC, 3065, Australia. Glenn.Ward@svha.org.au.|Clinical Chemistry, St Vincent's Hospital Melbourne, Fitzroy, 3065, Victoria, Australia. Glenn.Ward@svha.org.au.|Department of Medicine, St Vincent's Hospital, University of Melbourne, Fitzroy, 3065, Victoria, Australia. Glenn.Ward@svha.org.au.
authors.forename: Glenn M
authors.initials: GM
authors.lastname: Ward
authors.affiliation: Endocrine Centre, Austin Health, West Heidelberg, 3081, Victoria, Australia. g.jerums@unimelb.edu.au.|Department of Medicine, Austin Health, University of Melbourne, Heidelberg, 3084, Victoria, Australia. g.jerums@unimelb.edu.au.
authors.forename: George
authors.initials: G
authors.lastname: Jerums
mesh_terms: D000368:Aged; D001315:Australia / Q000453:epidemiology; D015415:Biomarkers; D015897:Comorbidity; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D048909:Diabetes Complications / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D015340:Epidemiologic Research Design; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D015203:Reproducibility of Results; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine