Introduction In 2014 therapeutic drug monitoring (TDM) for antiTNF was introduced to the Royal London Hospital. Approximately 170 IBD patients per month receive infliximab or adalimumab. Previous data have shown TDM and optimised antiTNF prescribing improves clinical outcomes.1 We audited the impact of TDM on cost-effectiveness and clinical outcome after 9 months compared to predictions we made prior to the introduction of this service.2
Methods All IBD patients on antiTNF who had TDM between November 2014 and July 2015 were identified retrospectively using pathology records. Ideal standards of care were defined prospectively for different drug and antibody results. Actual clinical actions and outcomes 3 months after TDM were recorded and compared with the defined ideal standards of care.
Results 160 tests on 133 patients were identified in the study period including 74 patients on infliximab and 59 patients on adalimumab. 88% patients had Crohn’s disease and 10% had ulcerative colitis. Escalated dosing regimens (increased dose or frequency) were prescribed in 48% patients.
In patients on escalated doses, 13% IFX and 33% ADA had unrecordably high drug levels. A further 8% IFX patients on escalated doses were in deep clinical remission (CRP < 5 and HBI or Mayo score 0–1). Reducing these prescriptions to standard dosing alone could have saved £166800 over 12 months. However, only 3/19 patients had dose reductions within 3 months, saving £27980. Neutralising antibodies were identified in 12% IFX and 9% ADA patients.
Appropriate cessation of antiTNF took place in 75% IFX and 20% ADA patients. Appropriate dose escalation only took place in 36% IFX and 6% ADA patients with low levels and no antibodies.
Conclusion Empiric prescribing based on clinical assessment alone leads to sub-optimal drug levels in around 50% patients. The introduction of antiTNF TDM has allowed rational dose optimisation with immediate savings and clinical benefits. In routine practice, delays in interpreting TDM impacted on dose optimisation and wasted resources. These data have led to local changes in practice to ensure all results are acted on promptly.
References 1 Vaughn BP, Sandborn WJ, Cheifetz AS. Biologic concentration testing in IBD. Inflamm Bowel Dis 2015;21(6):1435–1442.
2 Tandiari T, et al. PTH-083 Selective monitoring of antiTNF drug levels and antibodies will reduce short-term prescribing costs and provide early personalised tailoring of antiTNF therapy in routine IBD practice. Gut 2015;64(Suppl 1): A443.
Disclosure of Interest P. Harrow: None Declared, C. Skinner: None Declared, T. Hoque: None Declared, A. Ibarra: None Declared, J. Lindsay Grant/research support from: MSD, Takeda and Hospira, Consultant for: MSD, Takeda, Abbvie, Napp, Hospira and Celltrion