title: Estimating glomerular filtration rate in black South Africans by use of the modification of diet in renal disease and Cockcroft-Gault equations.
abstract: BACKGROUND
  The 4-variable Modification of Diet in Renal Disease (4-v MDRD) and Cockcroft-Gault (CG) equations are commonly used for estimating glomerular filtration rate (GFR); however, neither of these equations has been validated in an indigenous African population. The aim of this study was to evaluate the performance of the 4-v MDRD and CG equations for estimating GFR in black South Africans against measured GFR and to assess the appropriateness for the local population of the ethnicity factor established for African Americans in the 4-v MDRD equation.
  
  
  METHODS
  We enrolled 100 patients in the study. The plasma clearance of chromium-51-EDTA ((51)Cr-EDTA) was used to measure GFR, and serum creatinine was measured using an isotope dilution mass spectrometry (IDMS) traceable assay. We estimated GFR using both the reexpressed 4-v MDRD and CG equations and compared it to measured GFR using 4 modalities: correlation coefficient, weighted Deming regression analysis, percentage bias, and proportion of estimated GFR within 30% of measured GFR (P(30)).
  
  
  RESULTS
  The Spearman correlation coefficient between measured and estimated GFR for both equations was similar (4-v MDRD R(2) = 0.80 and CG R(2) = 0.79). Using the 4-v MDRD equation with the ethnicity factor of 1.212 as established for African Americans resulted in a median positive bias of 13.1 (95% CI 5.5 to 18.3) mL/min/1.73 m(2). Without the ethnicity factor, median bias was 1.9 (95% CI -0.8 to 4.5) mL/min/1.73 m(2).
  
  
  CONCLUSIONS
  The 4-v MDRD equation, without the ethnicity factor of 1.212, can be used for estimating GFR in black South Africans.
authors.affiliation: Department of Chemical Pathology and NHLS, University of the Witwatersrand, Johannesburg, South Africa. manuel.vandeventer@gmail.com
authors.forename: Hendrick E
authors.initials: HE
authors.lastname: van Deventer
authors.forename: Jaya A
authors.initials: JA
authors.lastname: George
authors.forename: Janice E
authors.initials: JE
authors.lastname: Paiker
authors.forename: Piet J
authors.initials: PJ
authors.lastname: Becker
authors.forename: Ivor J
authors.initials: IJ
authors.lastname: Katz
mesh_terms: D000328:Adult; D001741:Black or African American; D000368:Aged; D000369:Aged, 80 and over; D044383:Black People; D004032:Diet; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D011446:Prospective Studies; D051436:Renal Insufficiency, Chronic / Q000178:diet therapy / Q000208:ethnology* / Q000503:physiopathology; D013019:South Africa / Q000453:epidemiology