PWE-018 New guidance on therapeutic drug monitoring; potential clinical and cost implications

Introduction Biologic drugs are effective treatments in IBD, the use of therapeutic drug monitoring (TDM) is rapidly becoming part of routine clinical practice. The American Gastroenterology Association (AGA) and the Australian Gastroenterology Association have recently published guidance recommending the use of therapeutic drug monitoring in clinical practice. Recommendations on the minimum trough level for Infliximab differ between these two guidelines. The AGA recommends a level >5 µg/ml, whilst the Australian guidance suggests >3 µg/ml. To date there are no published recommendations from ECCO or BSG. In patients with active disease and sub-therapeutic trough levels we shorten the dose interval from 8 to 4 weeks. Aim To review the clinical and cost implications of introducing these guidelines into clinical practice at a large district general hospital Methods We maintain a prospective IBD database and have used TDM routinely since2014. Data on the use of TDM from 2016 to 2017 were reviewed. Age, Sex, disease type, and disease activity were reviewed. Results of drug levels in the active disease and remission group were compared and the cost implications of intensifying drug treatment to achieve recommended trough levels calculated. The costs were calculated for escalating all patients below recommended levels to dosing every 4 weeks. Results Biosimilar Infliximab (Remsima) trough level data was available for 167 patients. Mean age=42, Range 18–81. 133 (80%) had Crohn’s disease and 34 (20%) UC. 118 had inactive disease at the time of TDM, whilst 49 had active disease. Of those with inactive disease 78/118 (66%) had an Infliximab TL Conclusions In our cohort of 167, 62% (n=104) of patients had a TL below the recently published recommended guidelines (5 µg/ml) yet were in a clinical remission. Therefore following these guidelines would lead to a significant increase in drug spend which may not translate into improved clinical outcomes; since in this cohort only 24% with sub-therapeutic levels had active disease. Escalating only those with active disease may represent a more acceptable financial solution but too will lead to an increase in drug spend.