Glomerular filtration rate equations do not accurately predict vancomycin trough concentrations in pediatric patients

The Bedside Chronic Kidney Disease in Children (CKiD) equation was developed using data from children with chronic kidney disease. Some institutions are using this equation in all pediatric patients, regardless of renal function, to adjust medications. No data have shown that the Bedside CKiD equation is equivalent or better than the Schwartz equation in estimating glomerular filtration rate (GFR) in pediatric patients with normal renal function.

To compare GFR estimates using the Bedside CKiD and Schwartz equations and determine if either offers sufficient vancomycin dosing guidance in hospitalized pediatric patients.

This retrospective review at a single-center, academic, pediatric hospital included patients 2 to 12 years old with a steady-state vancomycin trough collected between January 1, 2010 and December 31, 2011. Patients with acute kidney injury or lacking essential data (e.g., height and serum creatinine), were excluded. An estimated GFR (eGFR) was calculated using the Schwartz and Bedside CKiD equations. Pearson correlations and linear regressions compared the eGFR values and vancomycin troughs.

A total of 50 vancomycin troughs were analyzed. There was a weak relationship between the eGFR and troughs for the Schwartz equation (r (2) = 0.028) and Bedside CKiD equation (r (2) = 0.028). A weak relationship between serum creatinine and troughs was observed (r (2) = 0.132). Limitations include small sample size and retrospective design.

Neither equation correlates well with vancomycin troughs, suggesting that therapeutic monitoring remains important. Better GFR estimation methods are needed in pediatrics to aid appropriate dosing of renally eliminated medications.