title: Monitoring kidney function in type 2 diabetic patients with incipient and overt diabetic nephropathy.
abstract: OBJECTIVE
  The purpose of this study was to assess agreement between glomerular filtration rate (GFR) and the decline in GFR estimated with the Modification of Diet in Renal Disease (MDRD) Study Group equation or the Cockcroft-Gault formula and measured by the plasma clearance of 51Cr-EDTA.
  
  
  METHODS
  We followed a cohort of 156 microalbuminuric type 2 diabetic patients for 8 years with four measurements of GFR and another cohort of 227 type 2 diabetic patients with overt diabetic nephropathy for 6.5 (range 3-17) years with seven (3-22) measurements of GFR.
  
  
  RESULTS
  For patients with microalbuminuria, mean +/- SD baseline GFR was 117 +/- 24 measured, 92 +/- 20 estimated (MDRD equation), or 103 +/- 24 ml x min(-1) per 1.73 m2 estimated (Cockcroft-Gault formula) (both P < 0.001); 95% limits of agreement were -66.1 to 20.3 (MDRD equation) and -58.7 to 30.7 (Cockcroft-Gault formula). The rate of decline in GFR was 4.1 +/- 4.2 measured, 2.9 +/- 2.8 estimated (MDRD equation), or 3.4 +/- 3.2 ml x min(-1) per 1.73 m2 estimated (Cockcroft-Gault formula) (both P < 0.001). For patients with overt nephropathy, baseline GFR was 84 +/- 30 measured, 73 +/- 24 estimated (MDRD equation), or 81 +/- 28 ml x min(-1) per 1.73 m2 estimated (Cockcroft-Gault formula) (both P < 0.001) with 95% limits of agreement -47 to 25 (MDRD equation) and -39 to 33 (Cockcroft-Gault formula). The rate of decline in GFR was 5.2 +/- 4.1 measured, 4.2 +/- 3.8 estimated (MDRD equation), and 4.6 +/- 4.1 ml x min(-1) per 1.73 m2 estimated (Cockcroft-Gault formula) (both P < 0.001).
  
  
  CONCLUSIONS
  Particularly in microalbuminuric (hyperfiltering) patients, GFR is significantly underestimated with wide limits of agreement by the MDRD equation as well as by the Cockcroft-Gault formula. The rate of decline in GFR is also significantly underestimated with both equations. This makes GFR estimations based upon these equations unacceptable for monitoring kidney function in type 2 diabetic patients with incipient and overt diabetic nephropathy.
authors.affiliation: Steno Diabetes Center, Gentofte, Denmark. pro@steno.dk
authors.forename: Peter
authors.initials: P
authors.lastname: Rossing
authors.forename: Kasper
authors.initials: K
authors.lastname: Rossing
authors.forename: Peter
authors.initials: P
authors.lastname: Gaede
authors.forename: Oluf
authors.initials: O
authors.lastname: Pedersen
authors.forename: Hans-Henrik
authors.initials: HH
authors.lastname: Parving
mesh_terms: D000419:Albuminuria / Q000453:epidemiology; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D003928:Diabetic Nephropathies / Q000145:classification / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods; D013997:Time Factors
chemical_list: D003404:Creatinine