Analysis of errors in tacrolimus blood level measurements related to different methods of sampling blood through a central venous catheter

Abstract

 Tacrolimus is usually administered continuously through one lumen of a double-lumen central venous catheter (CVC) in allogeneic hematopoietic stem cell transplantation. Although blood samples for therapeutic drug monitoring are taken through the other CVC lumen in children, the drug-concentration result is often falsely elevated. In order to reduce measurement errors obtained when collecting blood samples through a CVC, we retrospectively compared two blood-sampling methods: the standard method and a “flushing method,” in which the lumen is flushed with 5 mL saline before drawing blood. The flushing method significantly reduced measurement errors (median Rc [the ratio of the drug concentration measured in the blood sample collected through the CVC to that collected using venipuncture], 1.019 vs 1.142; p=1.8×10−10). In conclusion, the flushing method was an effective and more accurate means of monitoring blood concentration without the need for frequent venipuncture.