Introduction
Therapeutic Drug Monitoring (TDM), measuring serum drug levels (DL) and antibodies, is an established tool to optimise the efficacy of anti-TNF medicines in the treatment of patients with inflammatory bowel disease (IBD) via adaptation of drug frequency and dose. TDM is generally performed in proactive (pTDM) or reactive (rTDM) strategies. In rTDM, DLs are performed when disease relapses or flare occurs. In pTDM, DLs are measured routinely as part of ongoing clinical review to enable manipulation of drug dosing to achieve DLs within specified therapeutic ranges.1,2,3 While TDM testing is recommended in clinical practice guidelines, there is a lack of data demonstrating the impact of TDM on clinically meaningful outcomes and it is unclear whether the type of testing strategy employed is important . Reducing excessive steroid exposure for these patients remains an important clinical outcome in the UK .4
Aims & Methods
The aim of this study was to assess the impact of pTDM and rTDM on steroid exposure for our local, Infliximab (IFX) treated, IBD population.
Patient data was identified using the West of Scotland NHS Safe Haven. Patients with IBD, treated with IFX, and undergoing TDM were included and allocated to a pTDM or rTDM group based on the clinical indication of first TDM test. DL and prednisolone exposure data were extracted and reviewed from January 2018-December 2019. Annual steroid excess was defined as 2 or more steroid prescriptions in 12 months.1 SPSS was used to perform a Chi-squared and Mann-Whitney U tests.
Results
197 patients were included (pTDM:172, rTDM:25). 210 corresponding DLs were available. The median pTDM DL was 5.35ug/ml, and 5.25ug/ml in the rTDM group. No difference was seen in DLs between the 2 groups (p=0.828). 91/197 (46.2%) were exposed to steroids in the 2 year period, 63/197 (31.9%) in excess. 17/25 (68%) of rTDM patients were exposed to steroid compared to 74/172 (43%) in the pTDM group (p=0.19). 14/25 (56%) of rTDM patients were exposed to steroid in excess compared to 49/172 (28.5%) in the pTDM group (p=0.006).
Conclusion
In this retrospective cohort steroid exposure and excess was lower in patients undergoing pTDM compared to rTDM. Further work exploring the factors influencing this observation, in larger, prospective studies is required to fully understand the impact of TDM on patient care. The relationship between TDM and other clinical outcomes, including hospital admissions, is underway in this cohort.
References
- Lamb CA et al. Gut 2019;68:s1-s106
- Raine T et al. JCC 2022;16(1):2-17
- Torres J et al. JCC 2020;14(1):4-22
- Rosiou K et al. Aliment Pharmacol Ther. 2022;56:L501-509