Infliximab and adalimumab concentrations and anti-drug antibodies in inflammatory bowel disease control using New Zealand assays.

Background: Therapeutic drug monitoring of anti-tumour necrosis factor (TNF) drugs and anti-drug antibodies (ADA) is now recommended in the treatment of inflammatory bowel disease. However, assay types and drug concentration thresholds are still debated.

Aim: To correlate inflammatory bowel disease activity in a New Zealand cohort with trough concentrations of infliximab and adalimumab, and ADA using locally developed competitive-binding enzyme-linked immunosorbent assays (ELISA) to establish threshold concentrations.