Evaluating the necessity of two-point sampling for vancomycin area under the curve in follow-up therapeutic drug monitoring.

Abstract

Objective: While both peak and trough (two-point) sampling are recommended to estimate the area under the concentration-time curve (AUC) for vancomycin, one-point sampling may reduce clinical burden. This study aimed to identify patient populations requiring two-point sampling by examining risk factors associated with AUC discrepancies between one- and two-point sampling during follow-up therapeutic drug monitoring (TDM).

Method: This multicenter retrospective observational study included adult patients who received vancomycin from September 2020 to December 2023 and underwent two-point sampling at both initial and follow-up TDM. AUC was estimated using the Practical Antimicrobial TDM (PAT) version 4.0, and creatinine clearance (CLcr) was calculated using the Cockcroft-Gault equation. One- and two-point follow-up AUCs were compared using previously entered two-point concentrations from initial TDM. Patients were divided into a discrepancy group (AUC difference ≥10 %) and a non-discrepancy group. Risk factors were identified by univariate and multivariate analysis.

Results: AUC values from one- and two-point sampling in 256 cases were highly correlated (r² = 0.965, p < 0.001). Seventeen cases (6.6 %) showed discrepancies ≥10 %. Multivariate analysis identified BMI ≥25 kg/m² (OR = 6.946, p = 0.001), CLcr <50 mL/min (OR = 5.863, p = 0.002), and ΔCLcr ≥10 mL/min (OR = 4.444, p = 0.012) as significant risk factors.

Conclusion: Although one- and two-point AUCs showed strong correlation, discrepancies ≥10 % were more likely in patients with elevated BMI or impaired/unstable renal function. This suggests that two-point sampling may be essential for these patients to ensure accurate dosing of vancomycin during follow-up TDM.