Assessment of minimum discard volume for central venous catheter sampling: Validation via busulfan therapeutic drug monitoring in pediatric transplant patients

Purpose

Frequent blood sampling in pediatric patients, particularly during hematopoietic stem cell transplantation (HSCT), can lead to significant cumulative blood loss and increase the risk of iatrogenic anemia. This study aimed to evaluate whether reducing the discard volume prior to blood sampling affects the accuracy of plasma Busulfan concentration measurements in this vulnerable population. Patients and methods: This prospective cohort study enrolled thirteen pediatric patients receiving HSCT at a tertiary children's hospital in China between July and October 2024. Blood samples were collected via double-lumen central venous catheters at seven time points (T0-T6) after the fourth dose of Busulfan, using four different discard volumes (1, 2, 3, and 4 mL). Each patient contributed repeated measurements under all four discard-volume conditions, resulting in 364 samples. Paired analyses were used to account for the within-patient repeated-measures design, and AUC non-inferiority was assessed against the prespecified 6% margin using the lower bound of the two-sided 95% confidence interval for the paired differences.