Creatinine clearance in selection of living kidney donor among the Malaysian population: is it safe?

BACKGROUND: Assessment of donor renal function is made by the measurement of Glomerular Filtration Rate (GFR). Exogenous markers are preferred over creatinine clearance and are widely used for measuring GFR. However, they are difficult to obtain, costly and laborious. This is a study to look into the safety and accuracy of creatinine clearance for renal assessment among the living kidney donors in the Malaysian population. METHODS: This is a retrospective, single-centre study comprising 105 living kidney donor candidates from the year 2007 to 2020. By comparing against 51-Chromium ethylenediamine-tetraacetic acid (51Cr-EDTA), we analysed creatinine clearance for correlation, bias, precision and accuracy. RESULTS: The study group had a mean age of 45.68 ± 10.97 years with a mean serum creatinine of 64.43 ± 17.68 µmol/L and a urine volume of 2.06 ± 0.83 L. Mean measured GFR from 51Cr-EDTA was 124.37 ± 26.83 ml/min/1.73m2 whereas mean creatinine clearance was 132.35 ± 38.18 ml/min/1.73m2. Creatinine clearance overestimated 51Cr-EDTA significantly with a correlation coefficient of 0.48 (p < 0.001) and an accuracy of 78.10% and 64.0% within 30% and 20% respectively of 51Cr-EDTA. CONCLUSION: Creatinine clearance is an acceptable and affordable alternative for donor renal assessment in the absence of exogenous markers with an emphasis on adequate urine collection followed by using measured GFR in selected cases.

Utility of Estimated Glomerular Filtration Rate Equations in Assessing Renal Allograft Function: Are They Accurate?

Creatinine clearance (CrCl) is more accurate than other methods when assessing renal allograft function, but it is inconvenient for patients. In clinical practice, renal allograft function is often estimated using estimated glomerular filtration rate (GFR) equations. This cross-sectional study compared agreement between CrCl and serum creatinine-based equations among renal transplant recipients (RTRs) attending a transplant clinic in a tertiary center. Six equations (Cockcroft-Gault, Walser's, Nankivell, abbreviated Modification of Diet in Renal Disease [MDRD], Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI], and European Kidney Function Consortium[EKFC]) were included in the analysis. The bias, precision, and accuracy of each equation were determined. Correlation analysis was performed by determining the correlation coefficient and plotting Bland-Altmann plots. A total of 165 subjects were included in this study. Mean serum creatinine was 112.03 ± 38.67 µmol/L, and mean CrCl was 58.44 ± 21.24 mL/min/1.73 m2. Walser's equation showed strongest correlation, lowest bias, and highest accuracy of the proportion of estimated GFR falling within ±30% of CrCl, followed by the 4-variable MDRD equation. All 6 equations systematically underestimated GFR among RTRs. Walser's equation showed the best estimation of GFR, suggesting that it may be the formula of choice to estimate GFR among RTRs.

The Utility of Combined Urine Urea and Creatinine Clearance for Pretransplant Renal Function Assessment.

BACKGROUND: Evaluation of donor renal function as glomerular filtration rate (GFR) is a crucial part of pretransplant workup. Most guidelines recommend measured GFR (mGFR) using exogenous markers with creatinine clearance (CrCl) as an alternative. However, exogenous markers are difficult to obtain and perform, and CrCl may overestimate GFR. OBJECTIVE: We explore the use of CrCl and combined urea and creatinine clearance as an alternative for GFR assessment. METHODS: A retrospective study involving 81 kidney donors from 2007 to 2020, with mGFR collected by chromium 51-labeled ethylenediaminetetraacetic acid (51Cr-EDTA) and CrCl and combined urea and creatinine clearance. We analyzed the performance of CrCl and combined urea and creatinine clearance against 51Cr-EDTA. Adequacy of urine volume was taken into consideration. RESULTS: A total of 81 candidates with a mean age of 44.80 ± 10.77 years were enrolled. Mean mGFR from 51Cr-EDTA was 123.66 ± 26.91 mL/min/1.73 m2, and combined urea and creatinine clearance and CrCl were 122.13 ± 47.07 and 133.40 ± 36.32 mL/min/1.73 m2, respectively. CrCl overestimated 51Cr-EDTA. Though combined urea and creatinine clearance had minimal bias, it had a lower correlation coefficient (0.25 vs 0.43), lower precision (49.51 vs 38.10), and slightly lower accuracy within 30% of 51Cr-EDTA (74.07% vs 76.54%). CONCLUSIONS: Combined urea and creatinine clearance did not improve the performance of CrCl. Nevertheless, it can potentially be used as first-line GFR assessment, followed by mGFR in selected donors, to ascertain threshold of safe kidney donation. A stringent urine collection method is essential to ensure accurate measurement.