P112 Impact of therapeutic drug monitoring on outcomes for patients with inflammatory bowel disease

Introduction Anti-tumour necrosis factor α biological drugs have proven efficacy in the management of inflammatory bowel disease (IBD). Among infliximab and adalimumab treated cohorts, primary non response occurs in up to 30% and secondary non response occurs in up to 46% of patients. Therapeutic drug monitoring (TDM) is a useful tool for optimising drug dosing and modification. The aim of this study is to assess the appropriateness and effectiveness of TDM in IBD patients in a large UK district general hospital. Methods This was a retrospective study. Patients with Crohn’s disease (CD) and Ulcerative Colitis (UC) on infliximab and adalimumab were identified from 2017 – 2019. Clinician’s response to TDM results were monitored. CRP and faecal calprotectin up to 3 months before and after TDM with appropriate management were recorded. Hospital admission and surgery rates were compared between the TDM and non-TDM cohorts. Wilcoxon signed rank and Mann-Whitney test were applied to determine statistical significance. Results 364 patients were included (281 CD, 73 UC, 10 IBD-unclassified; 204 on infliximab, 160 on adalimumab). 209 (57.4%) patients were tested for TDM at least once during their follow up. Indications for TDM included proactive (85/209), worsening symptoms (103/209), worsening biochemistry (15/209) and worsening endoscopy (6/209). The median infliximab level was 5µg/mL. Antibodies to infliximab were present in 34% of patients. The median adalimumab level was 9µg/mL. Antibodies to adalimumab were present in 22% of patients. 88.5% of patients had an appropriate management plan based on their TDM results. This included no change (118/209), increase in dose/frequency (33/209), adding an immunomodulator (13/209), switching within class (22/209), switching out of class (17/209) and drug discontinuation (6/209). Mean CRP before TDM was 22.5 and after TDM 5.2. TDM followed by appropriate management elicited a significant reduction in CRP (Z = -5.1, P Conclusion CRP and faecal calprotectin significantly reduced after TDM and appropriate management. Hospital admissions and surgery were significantly less in the TDM group. There are limitations due to retrospective design and confounding factors; we acknowledge the TDM group tended to have closer monitoring, which may have led to better outcomes. This study demonstrates TDM as a powerful tool in personalised care for inflammatory bowel disease.