Accuracy of predicting the vancomycin concentration in Japanese cancer patients by the Sawchuk-Zaske method or Bayesian method.

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In cancer patients treated with vancomycin, therapeutic drug monitoring is currently performed by the Bayesian method that involves estimating individual pharmacokinetics from population pharmacokinetic parameters and trough concentrations rather than the Sawchuk-Zaske method using peak and trough concentrations. Although the presence of malignancy influences the pharmacokinetic parameters of vancomycin, it is unclear whether cancer patients were included in the Japanese patient populations employed to estimate population pharmacokinetic parameters for this drug. The difference of predictive accuracy between the Sawchuk-Zaske and Bayesian methods in Japanese cancer patients is not completely understood. To retrospectively compare the accuracy of predicting vancomycin concentrations between the Sawchuk-Zaske method and the Bayesian method in Japanese cancer patients. Using data from 48 patients with various malignancies, the predictive accuracy (bias) and precision of the two methods were assessed by calculating the mean prediction error, the mean absolute prediction error, and the root mean squared prediction error. Prediction of the trough and peak vancomycin concentrations by the Sawchuk-Zaske method and the peak concentration by the Bayesian method showed a bias toward low values according to the mean prediction error. However, there were no significant differences between the two methods with regard to the changes of the mean prediction error, mean absolute prediction error, and root mean squared prediction error. The Sawchuk-Zaske method and Bayesian method showed similar accuracy for predicting vancomycin concentrations in Japanese cancer patients.