Reliability evaluation of four different assays for therapeutic drug monitoring of infliximab levels.

All four assays seem suitable for therapeutic drug monitoring of infliximab. Promonitor and Q-Inflixi had the best agreement, making those assays fully interchangeable. Systematic biases between Lisa-Tracker with Promonitor and Q-Inflixi suggest that these assays should not be interchanged during the follow up of an individual patient.