Estimation of residual glomerular filtration rate and renal Kt/Vurea from creatinine clearance in end-stage renal disease patients. The Netherlands Cooperative Study on the Adequacy of Dialysis.

Residual glomerular filtration rate (rGFR) and renal Kt/Vurea are important parameters in clinical practice and in cohort studies. The calculation of these parameters requires analysis of urea in a 24-hour urine collection and in a simultaneously obtained plasma sample. In clinical practice, urea clearance is not always determined, but creatinine clearance usually is. The aim of the present study was to assess how well rGFR and renal Kt/Vurea can be estimated from creatinine clearance in end-stage renal disease (ESRD) patients. Of new Dutch ESRD patients, 365 were consecutively included in this study at the start of their chronic dialysis treatment. The estimation models were based on a random sample of two-thirds of the patients; the models were validated on the remaining one-third. We built models for pre-dialysis and peritoneal dialysis (PD) patients together (pre + PD group), and separate models for hemodialysis (HD) patients. Mean measured rGFR of pre + PD patients in the validation group was 6.3 mL/minute. The limits of agreement (LoAs) between estimated and measured rGFR were within -1.5 and +1.5. Mean measured rGFR in HD patients was 3.1 mL/minute (LoAs: -0.3 and +0.3). These relatively small limits of agreement reveal that, should urea clearance be missing, rGFR can be estimated by a formula in which creatinine clearance and 24-hour urine production are included. The estimation of renal Kt/Vurea from creatinine clearance was less precise.