Abstract
Background and Aims
All living kidney donors undergo assessment of renal function by evaluation of Glomerular Filtration Rate (GFR). 51Cr-EDTA is one of the most widely used marker for measuring GFR but it is hampered by cost and laboriousness as well as not being widely available in Malaysia. Measuring 24-hour urine for creatinine clearance (Ccr) is a common alternative when exogenous filtration markers are not available. Ccr suffers from over/underestimation of measured GFR (mGFR) due to errors in urine collection and tubular secretion of creatinine. This is a study to compare the correlation of Ccr against 51Cr-EDTA in measuring GFR among the living donors in Malaysian population.
Method
This is a cross-sectional, single-centre study of a cohort of living kidney donor candidates from January 2007 to March 2019. All candidates who had mGFR done with both 51Cr-EDTA and Ccr in University Malaya Medical Centre were enrolled. Special consideration was taken to account for adequate urine sampling for Ccr. Clinical data was analysed for correlation, bias, precision and accuracy between Ccr and 51Cr-EDTA.
Results
A total of 83 living kidney donors with a mean age of 45.60 ± 11.06 years and body mass index (BMI) of 24.36 ± 4.03 were enrolled. Female comprised 74.7% of the donors while Chinese, Malay and Indian accounted for 67.5%, 20.5% and 7.2% of the donors respectively. The study group had a mean serum creatinine of 63.37 ± 16.00 umol/L with a urine volume of 2.03 ± 0.81 L (range 0.70 – 3.82). mGFR from 51Cr-EDTA was 125.56 ± 27.64 ml/min/1.73m2 (range 77.0 – 194.3) whereas calculated Ccr was 136.05 ± 36.15 ml/min/1.73m2 (range 75.32 – 280.06). The correlation coefficient between Ccr and 51Cr-EDTA is moderate (r = 0.43) (p < 0.01). Mean absolute bias between Ccr and 51Cr-EDTA was 10.59 ± 37.99 ml/min/1.73m2 (p < 0.05). The accuracy of Ccr within 30% of 51Cr-EDTA was 77.11%.
Conclusion
Our study showed that Ccr significantly overestimates mGFR compared to 51Cr-EDTA. However, there is a significantly moderate positive correlation between Ccr and 51Cr-EDTA. Thus, in the absence of 51Cr-EDTA, Ccr is a clinically acceptable alternative if utilized with care and understanding its limitations.
Influence of the background activity region selection on the measurement of glomerular filtration rate using the Gates method
