Accuracy of 4 Free Online Dosing Calculators in Predicting the Vancomycin Area Under the Concentration-Time Curve Calculated Using a 2-Point Pharmacokinetic Approach

Abstract

Background: Free online adaptive vancomycin dosing calculators are available to estimate area under the concentration-time curve (AUC), but the accuracy of predicting vancomycin AUC using these calculators compared with using a 2-point pharmacokinetic approach has not been described. Objective: To evaluate the accuracy of calculator-predicted AUC (cpAUC) using 4 free online calculators compared with reference AUC (rAUC), and to assess pharmacists’ impressions of the ease of use. Methods: Vancomycin AUC was estimated using (1) the reference method via the Sawchuk-Zaske method and linear-logarithmic trapezoidal rule using 2 steady-state postdistributional vancomycin serum concentrations and (2) 4 free online vancomycin dosing calculators including ClinCalc, VancoPK, TDMx, and DMC. Accuracy was calculated by dividing cpAUC by rAUC. Ease of cpAUC estimation was determined by using a 10-point Likert scale. Results: All 4 calculators had a median cpAUC accuracy ranging from 89% to 110%. Concordance between cpAUC and rAUC determinations of AUC <400 and > 600 mg·h/L occurred 63.3% to 71.4% and 74.5% to 78.6% of the time, respectively. Pharmacist investigators agreed that ClinCalc and VancoPK calculators were easiest to use. Conclusion and Relevance: cpAUC accuracy varied among the 4 calculators, but all consistently identified patients with an rAUC <400 mg·h/L and an rAUC > 600 mg·h/L at comparable frequencies. All 4 calculators demonstrated some imprecision based on their wide 95% CIs and potential inaccuracies in predicting an rAUC <400 mg·h/L or an rAUC > 600 mg·h/L. Clin Calc and VancoPK were most user friendly based on our pharmacists’ impressions.