Introduction It has been recognised that the measurement of anti-TNF drug concentrations and detection of anti drug antibodies may be useful in aiding decision making and therefore optimising clinical outcomes in patients on anti-TNF drugs in whom there is incomplete clinical response or loss of drug therapy.¹

Methods A total of 45 Crohn’s patients attending our tertiary referral IBD clinic had anti TNF drug concentrations and antidrug antibodies levels measured. The indications for testing were incomplete response or loss of response during therapy.

We measured drug levels and Anti Drug Antibody levels using the ELISA assay (Immunodiagnostik). Reference ranges for Infliximab >2.0 ug/ml therapeutic and Adalimumab >5.0 ug/ml therapeutic. Total drug antibody levels >10 AU/ml positive.

Results We present the patient demographics in Table 1.

Drug and ADA levels 44% (n = 20) had therapeutic levels and negative antibodies, 18% (n = 8) had therapeutic levels and positive antibodies, 22% (n = 10) had sub-therapeutic levels and negative antibodies and 16% (n = 7) had sub-therapeutic levels and positive antibodies.

Impact of results meaurement of drug and ADA led to change in management in 28/45 (62%) patients. 6 (13%) patients switched therapy,17 (38%) had dose escalation,17 (38%) no treatment change,5 (11%)other outcome.

Conclusion Measurement of anti-TNF drug concentrations and antibody status in our patients on Anti TNF resulted in change of management in 28/45 (62%) patients.

In the 17 patients with dose escalation in whom outcome was assessed 13 (76%) patients have responded.

Measurement of drug concentration and antibody status presents an possible option in the management of patients on anti-TNF who present with loss of response or incomplete response of treatment

Reference 1 Vande Casteele N, et al. The relationship between infliximab concentrations, antibodies to infliximab and disease activity in Crohn’s disease. GUT 2015 Oct;64(10):1539–45.

Disclosure of Interest S. Laird: None Declared, L. Caulfield: None Declared, L. Smith Conflict with: cook, boston and allergan, almirall, J. Winter Conflict with: almirall, reckitt-Benckisaer, ferring, shire, D. Gaya: None Declared, A. Morris Conflict with: Falk,Vifor