Evaluation of Serum Creatinine Concentration–Based Glomerular Filtration Rate Equations in Pediatric Patients with Chronic Kidney Disease

STUDY OBJECTIVE: To evaluate the accuracy of four equations based on serum creatinine concentration-the original Schwartz equation and the Leger, Bedside Chronic Kidney Disease in Children (CKiD), and Counahan-Barratt equations-for determining glomerular filtration rate (GFR) in pediatric patients with chronic kidney disease. DESIGN: Retrospective, observational, cross-sectional study. SETTING: Single-center, academic, outpatient pediatric nephrology clinic. PATIENTS: Fifty-three pediatric patients with stages 2-5 chronic kidney disease who completed GFR assessment with (125) I-iothalamate between January 2002 and January 2005. MEASUREMENT AND MAIN RESULTS: Data were collected from each patient's medical record. Glomerular filtration rate data were analyzed using 59 evaluations from the 53 pediatric patients. (125) I-iothalamate clearance was used as the index GFR. The Bedside CKiD and Counahan-Barratt equations outperformed the Schwartz and Leger equations when the index GFR was less than 60 ml/minute/1.73 m(2) ; the Schwartz and Counahan-Barratt equations performed best for index GFRs of 60 ml/minute/1.73 m(2) or greater. Overestimation was highest with the Schwartz and Leger equations (> 20% index GFR in 57.6% and 62.7% of patients, respectively). Underestimation was highest with the Bedside CKiD and Counahan-Barratt equations (> 20% index GFR in 30.5% and 28.8%, respectively). CONCLUSION: The new Bedside CKiD equation performed well for pediatric patients with moderate-to-severe chronic kidney disease, but less well for pediatric patients with mild disease. Additional studies are needed to develop more precise GFR equations using serum creatinine concentration.