Comparison of vancomycin area under the concentration-time curve (AUC) using two-point pharmacokinetics versus two open-access online single-concentration vancomycin calculators.

Abstract

Current vancomycin monitoring guidelines recommend the use of area under the concentration-time curve (AUC24 ) monitoring in patients with serious Methicillin-Resistant Staphylococcus aureus (MRSA) infections by utilizing either a Bayesian approach or first-order analytic equations. Several open-access websites exist that allow estimation of vancomycin AUC24 with the use of a single steady-state concentration. It is uncertain how these open-access calculators perform against guideline-recommended methods. The objective was to compare AUC24 estimates from two online, open-access, single-concentration vancomycin calculators compared with the two-point pharmacokinetic (2PK) method. AUC24 estimates were made using the 2PK reference method and the single-concentration vancomycin calculators, ClinCalc and VancoPK. The AUC24 estimates from the 2PK reference method were compared to the online calculators by assessing bias (median AUC24 difference) and precision (AUC24 difference ± 100 mg*h/L). Clinical precision was also assessed by characterizing the frequency that the 2PK reference method and the online calculators showed clinical disagreement based on the following AUC24 categories: (1) AUC24 < 400 mg*h/L; (2) AUC24 400-600 mg*h/L and (3) AUC24 > 600 mg*h/L. A total of 253 patients were included in the study. The AUC24 estimates from the ClinCalc and VancoPK single-concentration vancomycin calculators showed some bias and imprecision, though VancoPK appeared to have less. Clinical disagreement versus the 2PK reference method occurred in 31.2% and 19.4% of AUC24 estimates from the ClinCalc and VancoPK single-concentration vancomycin calculators, suggesting clinical imprecision. The AUC24 estimates from single-concentration, online vancomycin calculators showed some bias and imprecision in comparison to the 2PK method. Institutions should validate these online, trough-only calculators relative to a 2PK method in their patient populations prior to adoption as standard-of-care.