The diagnostic value of the Anti-Infliximab ELISA lies in its ability to stratify patients with subtherapeutic infliximab concentrations (< 1 μg/mL) in patients who need dose intensification or a drug (class) switch. Patients with low infliximab concentrations (< 1 μg/mL) and low ATI titers can benefit from infliximab dose intensification, as shown in several studies4, 5. However, the ATI titer of patients with low ATI titers undergoing a dose intensified treatment regimen must be adequally monitored. Patients that have high ATI titers are preferably switched to another drug, both within class or out of class. The course of ATI titers, based on the measurement of antibodies in at least two consecutive samples, is an important basis for the evaluation of the anti-drug antibody titer of the patient, rather than the absolute value of the titer.