Supplementary file 1_Assessment of minimum discard volume for central venous catheter sampling: Validation via busulfan therapeutic drug monitoring in pediatric transplant patients.docx

Paired differences between reduced discard volumes (1, 2, and 3 mL) and the 4 mL reference remained small, with 95% confidence intervals demonstrating consistent agreement. AUC non-inferiority analysis showed that the reduced discard-volume approaches remained within the prespecified 6% non-inferiority margin. ICC demonstrated excellent agreement between the reduced discard-volume conditions and the 4 mL reference for both individual time-point concentrations (ICC > 0.95) and AUC values.

Bland–Altman analysis showed consistent agreement, with differences evenly distributed within the calculated 95% limits of agreement.</p>Conclusion<p>A minimal discard volume of 1 mL demonstrated non-inferior accuracy compared with the standard 4 mL discard volume for determining plasma Busulfan levels and overall drug exposure during therapeutic drug monitoring. Implementing this approach may reduce cumulative discarded blood volume by up to 21 mL per patient during the seven sampling time points; however, the direct effect of reduced discard volume on anemia or transfusion requirements was not evaluated.

This study adhered to the STROBE guidelines for observational research, and no patient or public contribution was involved.</p>