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P399 Cost-effectiveness of utilising proactive Infliximab therapeutic drug monitoring for inflammatory bowel disease in routine clinical practice

J. Steen*1, M. McCormack2, C. McShane1, M. Healy2, V. Crowley2, U. Kennedy1, O. Hayes1, C. Dunne1, K. Hartery1, S. McKiernan1, F. MacCarthy1, D. Kevans1

1St. James Hospital, Gastroenterology, Dublin, Ireland, 2St. James Hospital, Biochemistry, Dublin, Ireland

Background

Therapeutic drug monitoring(TDM) is increasingly utilised in IBD practice to guide dosing of anti-TNFs. Proactive TDM assessment has not, however, been clearly shown to improve clinical outcomes compared with empiric dose optimisation. The aim of our study was to assess whether a proactive-TDM strategy, with the aim of dosing patients to an IFX-level in the therapeutic range, is a cost-effective strategy in routine practice.

Methods

IFX TDM has been available at SJH for a 1-year period. On a pilot basis, IBD patients receiving IFX had a single trough sample collected. IFX-levels and antibody-to-IFX concentrations (ADA) were determined. IFX levels from 3 to 7 µg/l were considered therapeutic. ADA of 50 AU/ml and above were considered significant . IFX treatment decisions based on TDM were documented. Costs/savings related to TDM use were estimated by documenting alterations to IFX regimens prompted by TDM and extrapolating annualised total dose increases / reductions.

Results

A total of 64 IBD patients were included, 51% male, 63% Crohn’s disease. Twenty-seven per cent, 43% and 30% of patients had a therapeutic, subtherapeutic and supratherapeutic IFX-level. n = 21 (33%) had significant ADA present. n = 35 patients (55%) patients had alterations to IFX dosing based on TDM: 23% had IFX dosing interval increased, 20% had IFX dosing interval decreased and 11% discontinued IFX therapy. The use of proactive-TDM was found to be cost-effective with annual savings of €70,083.34.

Conclusion

While Anti-TNF TDM has certainly been shown to be of value in the setting of loss of response to treatment, it remains unclear whether a proactive-TDM improves clinical outcomes. Our study suggests proactive TDM may at least be a cost-effective strategy.