Estimating glomerular filtration rate in black South Africans
Date
2010-04-16T07:03:42Z
Authors
Van Deventer, Hendrick Emanuel
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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 (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/1.73m2. Without the ethnicity
factor median bias was 1.9 (95% CI -0.8 to 4.5) mL/min/1.73m2.
Conclusion
The 4-v MDRD equation, without the ethnicity factor of 1.212, can be used for estimating
GFR in black South Africans.
Description
MMed, Chemical Pathology, Faculty of health Sciences, University of the Witwatersrand, 2009
Keywords
kidney filtration, kidney function, black South Africans