Selective Monitoring of Anti-TNF Drug Levels and Antibodies Will Reduce Short-Term Prescribing Costs and Provide Early Personalised Tailoring of Anti-TNF Therapy in Routine IBD Practice
Introduction: Clinical trial results suggest that measurement of antiTNF drug levels (ATL) and antibodies (ATA) may have a cost-saving as well as clinically beneficial effect in patients with IBD. We aimed to assess whether selective monitoring of ATL and ATA reduces prescribing costs and how it affects clinical
decisions in ordinary clinical practice.
Method: ATL and ATA were assayed in 47 (19%) of our 247 antiTNF-treated IBD patients (Crohn’s disease 41, ulcerative colitis 4 and pouchitis 2; (on infliximab 45, on adalimumab 2)) because of either secondary loss of response (n = 11) or a dosage of infliximab (IFX) exceeding 5 mg/kg every 8 weeks (n = 36). ATL and ATA were measured by automated LISA-TRACKER assay (Theradiag, France) at Viapath, St Thomas’ Hospital. For each patient, the outcomes of decisions about therapeutic strategy based on clinical assessment alone were compared against those based on assay results combined with clinical criteria. AntiTNF prescribing and surgery costs were predicted for the ensuing 4 months for the two decision-making strategies, assuming that infliximab phials were shared.
Results: Outcomes of the decisions taken are summarised in the Table. Prescribing costs estimated for the subsequent 4 months (17 weeks) for clinically based decisions were £225,825 and for assay based strategies were £209,772 (£3525 assay costs included). Predicted total cost savings using the assay based decisions,taking into account referrals for surgery and for trial drugs, were £16,053 in 4 months. Clinically based decisions led to more patients staying on antiTNFs, while assay-based decisions caused more patients to be switched to an alternative antiTNF, recruited to trials and referred for surgery. In 19/47 patients, both decision-making approaches gave the same outcome.
Conclusion: Measurement of antiTNF drug levels and antibodies in selected patients should produce short-term cost savings in ordinary clinical practice. Longer follow-up is needed to assess the clinical impact of the decisions made using these assays in combination with clinical criteria, but is likely to amplify the savings
they make possible.