Anti-TNF drugs, adalimumab (ADA) and infliximab (IFX), are effective treatments for ulcerative colitis (UC) and Crohn’s disease (CD). However, 30% of patients do not respond to treatment (primary non-response) and 40% lose response over time (loss of response). Loss of response is often due to development of antibodies to ADA (ATA) and IFX (ATI). While it is known that undetectable or low ATA/ATI titers (<200 ng/mL) are associated with better outcomes and high ATA/ATI titers (>1000 ng/mL) are associated with poor outcomes, the significance of intermediate ATA/ATI titers (200–999 ng/mL) is not well understood.