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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.

Context and objectiveIn the estimation of glomerular filtration rate (GFR), ethnicity is an important determinant. However, all existing equations have been built solely from Caucasian and Afro-American populations and they are potentially inaccurate for estimating GFR in African populations. We therefore evaluated the performance of different estimated GFR (eGFR) equations in predicting measured GFR (mGFR).MethodsIn a cross-sectional study, 93 healthy adults were randomly selected in the general population of Kinshasa, Democratic Republic of the Congo, between June 2015 and April 2016. We compared mGFR by plasma clearance of iohexol with eGFR obtained with the Modified Diet in Renal Disease (MDRD) equation with and without ethnic factor, the Chronic Kidney Disease Epidemiology (CKD-EPI) serum creatinine (SCr)-based equation, with and without ethnic factor, the cystatin C-based CKD-EPI equation (CKD-EPI SCys) and with the combined equation (CKD-EPI SCrCys) with and without ethnic factor. The performance of the equations was studied by calculating bias, precision and accuracy within 30% (P30) of mGFR.ResultsThere were 48 women and 45 men. Their mean age was 45.0±15.7 years and the average body surface area was 1.68±0.16m2. Mean mGFR was 92.0±17.2 mL/min/1.73m2 (range of 57 to 141 mL/min/1.73m2). Mean eGFRs with the different equations were 105.5±30.1 and 87.2±24.8 mL/min/1.73m2 for MDRD with and without ethnic factor, respectively; 108.8±24.1 and 94.3x20.9 mL/min/1.73m2 for CKD-EPI SCr with and without ethnic factor, respectively, 93.5±18.6 mL/min/1.73m2 for CKD-EPI SCys; 93.5±18.0 and 101±19.6 mL/min/ 1.73m2 for CKD-EPI SCrCys with and without ethnic factor, respectively. All equations slightly overestimated mGFR except MDRD without ethnic factor which underestimated by -3.8±23.0 mL/min /1.73m2. Both CKD-EPI SCr and MDRD with ethnic factors highly overestimated mGFR with a bias of 17.9±19.2 and 14.5±27.1 mL/min/1.73m2, respectively. There was a trend for better P30 for MDRD and CKD-EPI SCr without than with the ethnic factor [86.0% versus 79.6% for MDRD (p = 0.21) and 81.7% versus 73.1% for the CKD-EPI SCr equations (p = 0.057)]. CKD-EPI SCrCys and CKD-EPI SCys were more effective than creatinine-based equations.ConclusionIn the Congolese healthy population, MDRD and CKD-EPI equations without ethnic factors had better performance than the same equations with ethnic factor. The equations using Cys C (alone or combined with SCr) performed better than the creatinine-based equations.

Background: Cystatin C-based equations are used to estimate GFR. However, three cystatin C immunoassays are on the market. Difference in cystatin C assays could have strong consequences on the accuracy and precision of cystatin C-based equations. We have performed an analytical study of these three assays and studied potential differences between assays on the precision of cystatin C-based equations. Methods:We have studied imprecision, recovery, linearity and interferences of the three immunoassays (nephelometric assay from Siemens and turbidimetric assays from Dako and Gentian). The impact of differences in cystatin C assays has been studied for the equations published by Levey (Siemens assay) and Grubb (Dako assay). Results Conclusion:The Siemens and Gentian assays seem analytically more valid than the Dako assay for cystatin C determination. Differences in cystatin C assays can lead to significant differences in cystatin C-based equations. However, these differences seem less important than the differences observed with creatinine and creatininebased equations.

Background: Although screening programs for chronic kidney disease (CKD) may be of great value, these programs are not yet implemented in the Democratic Republic of Congo. This study focused on proteinuria and examined its prevalence in terms of the number needed to screen for the different risk factors of CKD. Such knowledge would guide the utility of population screening to prevent end-stage renal disease. Methods: A cross-sectional survey was conducted in Kinshasa on the Second World Kidney Day. A sample of 3,018 subjects was interviewed and the following measurements were performed: blood pressure, body mass index, glycemia and urine protein. Logistic regression analysis was used to identify determinants of proteinuria. Results: The prevalence of proteinuria was 17.1% (95% CI 15.8–18.6). Other CKD risk factors identified were: hypertension, diabetes mellitus, obesity and metabolic syndrome. To identify 1 case of proteinuria, one would need to screen 4 persons with diabetes, 5 persons with hypertension, 4 subjects having metabolic syndrome, 5 persons aged ≥72 years and 9 persons without any of the conditions mentioned above. Age, overweight and diabetes were the strongest factors associated with proteinuria. Conclusions: This study indicates that proteinuria and traditional risk factors for CKD are very prevalent in Kinshasa. Realistic policies to stem these conditions should be a public health priority.