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 ₁₂₅I-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. ₁₂₅I-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 m₂; the Schwartz and Counahan- Barratt equations performed best for index GFRs of 60 ml/minute/1.73 m₂ 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.