Serum creatinine (Scr)-based equations, particularly the Schwartz equation, are widely used to estimate glomerular filtration rate (eGFR) and guide drug dosing in pediatric intensive care unit (PICU) patients. However, Scr may be influenced by non-renal factors, potentially leading to inaccurate renal function assessment. Cystatin C–based equations like the Hoek equation may serve as a better tool to guide drug dosing in PICU patients. The objective of this study was to examine the concordance between eGFR estimated using the Schwartz and Hoek equations and to investigate its potential implications for drug dosing in PICU patients. This was a prospective study of PICU patients aged 1 month to 14 years receiving renally eliminated antibiotics. eGFR was calculated using both the Schwartz and Hoek equations. Analyses included the mean relative difference, mean absolute relative difference, concordance rates within 10% and 30%, and classification into renal function categories: Participants were grouped by eGFR range: less than 50 ml/min/1.73m2, between 50 and 130 ml/min/1.73m2, and greater than 130 ml/min/1.73m2 ml/min/1.73m2 ml/min/1.73m2 ml/min/1.73m2. Agreement between the two estimation methods was further evaluated using Bland–Altman and scatter plots. A total of 65 pediatric patients were included in the study. The Schwartz equation overestimated estimated glomerular filtration rate compared to the Hoek equations, with a mean relative difference of 37.5% and mean absolute relative difference of 46.3%. Only 15% of patients had estimated glomerular filtration rate estimates within 10%, and 46% within 30% of each other. The renal function classification agreement between equations was 58%. Notably, the Schwartz equation categorized 48% of patients as having augmented renal clearance, compared to only 18% using the Hoek equation. There is significant discordance between serum creatinine and cystatin C based estimated glomerular filtration rate estimates in critically ill pediatric patients. The Schwartz equation frequently overestimates renal function, which may lead to inappropriate dosing. Greater adoption of cystatin C based methods in the PICU setting could improve the estimation of the GFR and drug dosing.
Samman et al. (Fri,) studied this question.