Glomerular filtration rate (GFR) is the best index for kidney function; however, the applicability of GFR estimating equations in sub-Saharan African populations remains unclear. In a cross-sectional study of adults living in Kinshasa, Democratic Republic of Congo (n[210) and Abidjan, Ivory Coast (n[284), we evaluated the performance of creatinine and cystatin C-based equations using plasma clearance of iohexol as the reference standard. The race coefficient did not improve the performance of creatinine-based GFR estimates; in fact, both the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology (CKD-EPI) equations performed better without the race coefficient in participants with GFR ‡60 mL/min/1.73m 2. The CKD-EPI and Full Age Spectrum (FAS) equations were unbiased and had similar precision (SD of 17.9 versus 19 mL/min/1.73 m 2) and accuracy within 30% (P30, 86.7% versus 87.4%) in participants with GFR ‡60 mL/min/1.73m 2. Both equations performed poorly in the subgroup with measured GFR < 60 mL/min/1.73m 2 (n[80), but the FAS equation had smaller bias (L4.8 mL/min/1.73m 2 versus L7.7 mL/min/1.73m 2 for CKD-EPI) and higher P30 (56.3% versus 31.3% for CKD-EPI). The corresponding equations including cystatin C alone or in combination with creatinine had similar performance. In a sub-Saharan African population, adjustment for race did not improve the performance of GFR estimating equations. The creatinine-based FAS and CKD-EPI equations performed reasonably well and were comparable when GFR was ‡ 60 mL/min/1.73m 2. Cystatin C did not improve performance. The FAS equation may be preferable when GFR is < 60 mL/min/1.73m 2 , but this should be confirmed in larger studies.

Background: Normal kidney function or, more specifically, normal glomerular filtration rate (GFR) in men and women and its decline with age is still much debated today. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation has gender (and race) multiplication factors, accounts for a decline that starts at very young age and assumes that the mean GFR is as high as 120-130 ml/min/1.73 m² from a young age. The full age spectrum (FAS) estimated mean GFR is about 107 ml/min/1.73 m² at a young age and remains constant until the age of 40 years and then starts to decline both in men and women. The aim of this research study was to give more insight into ‘normal' GFR levels and the physiological decrease of kidney function with age and to use a meta-analysis to evaluate the mathematical construction of the FAS and the CKD-EPI equation. Methods: We conducted a meta-analysis of published GFR measurements in healthy Caucasian living potential kidney donors (n = 5,482, 46.8% men). Only publications dating from 2000 were selected to avoid the possible influence of body surface area changes in the last decades on the indexed GFR, expressed in ml/min/1.73 m². Results: We found that the mean GFR ≈ 107 ml/min/1.73 m² up to the age of 40 years, but renal decline begins beyond 40 years. No evidence could be found for any difference between men and women in the separate age groups. Conclusions: The current meta-analysis supports the mathematical form of the FAS equation, which matches the age/sex dependency of measured GFR for healthy potential living kidney donors.

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Background A new Chronic Kidney Disease Epidemiology equation without race variable has been recently proposed (CKD-EPIAS). This equation has neither been validated outside USA nor compared to the new European Kidney Function Consortium (EKFC) and Lund-Malmö Revised (LMREV) equations, developed in European cohorts. Methods Standardized creatinine and measured glomerular filtration rate (GFR) from the European EKFC cohorts (n = 13 856 including 6031 individuals in the external validation cohort), from France, (n = 4429, including 964 Black Europeans), from Brazil (n = 100), and from Africa (n = 508) were used to test the performances of the equations. A matched analysis between White Europeans and Black Africans or Black Europeans was performed. Results In White Europeans (n = 9496), both the EKFC and LMREV equations outperformed CKD-EPIAS (bias of -0.6 and -3.2, respectively versus 5.0 mL/min/1.73m², and accuracy within 30% of 86.9 and 87.4, respectively versus 80.9%). In Black Europeans and Black Africans, the best performance was observed with the EKFC equation using a specific Q-value ( = concentration of serum creatinine in healthy males and females). These results were confirmed in matched analyses, which showed that serum creatinine concentrations were different in White Europeans, Black Europeans, and Black Africans for the same measured GFR, age, sex and body mass index. Creatinine differences were more relevant in males. Conclusion In a European and African cohort, the performances of CKD-EPIAS remain suboptimal. The EKFC equation, using usual or dedicated, population-specific Q-values presents the best performance in the whole age range in the European and African populations included in this study.

Normal GFR values and descriptions of percentiles are now available for West Africa. As in Caucasians, no significant difference was observed between men and women. Moreover, the same age-associated decline in mGFR is also observed after 40 years of age, as in Caucasians.