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This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: clinchem.2007.099085v1 54/7/1197    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by van Deventer, H. E. Articles by Katz, I. J. Search for Related Content PubMed PubMed Citation Articles by van Deventer, H. E. Articles by Katz, I. J. Related Collections General Clinical Chemistry

Estimating Glomerular Filtration Rate in Black South Africans by Use of the Modification of Diet in Renal Disease and Cockcroft-Gault Equations

¹ Department of Chemical Pathology and NHLS, University of the Witwatersrand, Johannesburg, South Africa; ² Biostatistics Unit, South African Medical Research Council and School of Therapeutic Sciences, University of the Witwatersrand, South Africa; ³ Division of Nephrology, Chris Hani Baragwanath Hospital, University of the Witwatersrand, Johannesburg, South Africa.

^aAddress correspondence to this author at: Department of Chemical Pathology, Wits Medical School, 7 York Road, Parktown 2193, South Africa. E-mail manuel.vandeventer{at}gmail.com.

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 (⁵¹Cr-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 (P₃₀).

Results: The Spearman correlation coefficient between measured and estimated GFR for both equations was similar (4-v MDRD R² = 0.80 and CG R² = 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 m². Without the ethnicity factor, median bias was 1.9 (95% CI –0.8 to 4.5) mL/min/1.73 m².

Conclusions: The 4-v MDRD equation, without the ethnicity factor of 1.212, can be used for estimating GFR in black South Africans.

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