ESTIMATION OF TOTAL CREATININE CLEARANCE IS UNRELIABLE IN CHILDREN ONPERITONEAL-DIALYSIS

Objective: To test the reliability of creatinine clearance in children on peritoneal dialysis (PD). Design: Longitudinal, case-controlled. S etting: Routine clinic visits at the pediatric dialysis unit of the Un iversitatskinderklinik of Vienna. Patients:Eleven children (2-13 years , 10-55 kg) with end-stage renal disease on PD. Interventions: Creatin ine clearance (CCr) was determined by measuring creatinine excretion ( ECr) over 24 hours in both dialysate and urine. Each child had three t o five separate measurements of their CCr. At the same time we also ca lculated the Schwartz formula clearance from the patient's height and serum creatinine, using a modified correlate. Main Outcome Measures: R eliability of CCr was assessed by two approaches. First, we compared e ach serial measurement with the mean value for each patient and thereb y assessed the ''intramethodical'' variability. Second, we compared ea ch CCr with the simultaneous formula clearance and assessed the ''inte rmethodical'' disagreement. Results: Twenty-seven percent of the measu rements of CCr were classified as unreliable based on a comparison wit h the mean value for each patient. Reliability was closely correlated with residual renal function (p < 0.01); only 12% of the measurements in the anuric patients were classified as unreliable (vs 31% in the pa tients with residual renal function). The simultaneous formula clearan ce was less variable than the CCr. The formula clearance had a sensiti vity of 93% and a specificity of 60% for detecting unreliable values o f CCr. Conclusion: Estimation of total CCr is unreliable in pediatric patients on PD. A simultaneous formula clearance can be used to detect which values are unreliable.