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Published on: September 9, 2015
Real-World Comparison of Trough- and Online-Bayesian-Calculator-Derived AUC0-24/MIC Target Attainment for Vancomycin
Sufyan Alomair1, Zahra Alsultan1, Fatimah Alsultan1
1Department of Pharmacy Practice, College of Clinical Pharmacy, King Faisal University, Al-Ahsaa 31982, Saudi Arabia.
Abstract:
Introduction: The preferred PK/PD goal for vancomycin is now AUC0-24/MIC-guided dosing, which requires two blood samples, additional time, increased cost, and possibly specialized staff, potentially limiting its use. Our study compared vancomycin target attainment using trough versus single-sample Bayesian AUC0-24/MIC in critically ill patients, using a validated online calculator. Methods: This retrospective cohort study included adults aged ≥18 years with stable renal function who were receiving vancomycin. Exclusions were age under 18, unstable renal function, hemodialysis, missing data, or non-steady-state vancomycin. Steady-state troughs were obtained, and AUC0-24/MIC was calculated using ClinCalc. The primary endpoint was discordance in target attainment between trough (15-20 mg/L) and AUC0-24/MIC (400-600 mg·h/L). The secondary endpoint was AKI within 48 h of initiating vancomycin. Results: The mean trough was 14.8 ± 8.0 mg/L, and the mean AUC0-24/MIC was 499.7 ± 201.3 mg·h/L. Trough levels were within target in 20%, and AUC0-24/MIC in 67%. The 3 × 3 cross-tabulation showed a significant association (χ2 = 27.33, p < 0.001), but only fair agreement (Cohen's κ = 0.215) and a biased disagreement pattern (p < 0.001). Thirty-eight patients (38%) had "false alarming" results: trough < 15 mg/L despite AUC0-24/MIC ≥ 400 mg·h/L. Three patients (3.0%) showed "falsely reassuring" results: trough 15-20 mg/L with AUC0-24/MIC > 600 mg·h/L. The odds of supratherapeutic AUC0-24/MIC > 600 mg·h/L were tenfold higher in patients with trough 15-20 mg/L than in those below 15 mg/L (OR 10.24, p = 0.048). Conclusions: In critically ill ICU patients, calculator-derived AUC0-24/MIC showed significant discordance with single-trough vancomycin monitoring, primarily indicating apparent under-exposure by trough criteria in patients with adequate AUC0-24/MIC levels, which may lead to unnecessary dose escalation.
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