P-1238. AUC You Later: Comparison of Bayesian and First-Order Estimations of Vancomycin Area Under the Curve in Pediatrics

Abstract Background Consensus guidelines recommend therapeutic dose monitoring of vancomycin in pediatric patients to target a 24-hour area under the curve (AUC24) of 400-600 mg*hr/L. Recommended methods for estimation of AUC24 include the use of Bayesian software, with one or two concentrations, or first-order calculations using two concentrations. Limited data exist to compare these methods, particularly in pediatric populations. This study aimed to compare calculated AUC24 using first-order equations with two drug concentrations at steady state to Bayesian two- and one-concentration estimations.Figure 2:Bland Altman Plots and Categorical Agreement Methods This was a retrospective review of hospitalized pediatric patients (< 18 years) receiving intravenous vancomycin from 2020-2022. Patients were screened if they had two concentrations collected at steady-state within 96 hours of initiation. Patients with baseline renal dysfunction were excluded. Pharmacokinetic parameters and AUC24 were estimated using InsightRxTM Bayesian software incorporating the Colin model and first-order equations. Pearson’s correlation and clinical agreement (based on AUC24 classification) were used to compare methods (Figure 1). Bland-Altman plots were used to assess mean difference (MD) and 95% limits of agreement (LOA) (Figure 2). Results Overall, 196 patients (22 neonates, 17 infants, 114 children, and 42 adolescents) were included in the final analysis. Agreement was observed between linear and Bayesian two-concentration methods (84.2%; R2=0.723) and Bayesian two-concentration and one-concentration methods (82.7%, R2=0.839). Some variability was noted with 95% LOA -123 to 178 (MD=27 mg*hr/L) and -88 to 110 (MD=11 mg*hr/L), for the respective comparisons. Lower agreement was noted between linear and Bayesian one-concentration methods (73.9%, R2=0.544), and demonstrated the greatest amount of variability with 95% LOA -179 to 211 (MD=16 mg*hr/L). Conclusion Linear and Bayesian two-concentration methods demonstrated reasonable agreement with acceptable variability and may be considered comparable to estimate AUC24. Similarly, Bayesian two-concentration and one-concentration methods demonstrated reasonable agreement with acceptable variability, supporting the comparability of these methods to estimate AUC24. Disclosures All Authors: No reported disclosures