Background Monitoring of anti-drug antibodies (ATAS) or serum concentrations of adalimumab (ADA) in the treatment of inflammatory bowel disease (IBD) could provide an explanation for loss of efficacy and help optimise treatment and reduce healthcare costs.

Purpose To assess the cost savings by applying a decision algorithm based on measurement of ADA trough levels and ATAS in patients with IBD.

Material and methods A retrospective observational study of all IBD patients treated with ADA at the department of gastroenterology in a tertiary hospital in the past year was conducted. Plasma levels of ADA and ATAS by sandwich ELISA immunoassays were assessed, always immediately prior to the inclusion of the drug (Cmin). Variables included: pathology, treatment time, concentration of ADA and ATAS, clinical situation and concurrent medication. A clinical algorithm was used for reactive ADA concentration and antibody status to guide therapy decisions:

• ADA:

  • Subtherapeutic levels: < 5 µg/mL and ATAS negative –>require dose escalation;

  • < 5 µg/mL and ATAS positive–>switch;

  • Therapeutic levels: ≥5–8 µg/mL –> no dose change (independently of ATAS);

  • Supratherapeutic levels: >8 µg/mL –>require increase the dosing interval (independently of ATAS).

• ATAS:

  • Negative: <5 AU/mL.

  • Positive: >5 AU/mL.

Results Our recommendation applying the algorithm is the following: of these 66 patients, 14 patients required dose escalation (cost €169,302), 29 patients required increase in the dosing interval (cost saving €181 714), 14 patients required no dose change and 9 switched to another TNF inhibitor (cost saving €34,638). The cost per sample for the ELISA plate kit was €3600 and the total cost saving after applying the algorithm was €43 446.

Conclusion This study indicates that routine monitoring of drug levels and ATAS is cost-beneficial in clinical practice and thereby improves the personalisation of the decision making process.

References and/or acknowledgements Ordás I, Feagan BG, Sandborn WJ. Therapeutic drug monitoring of tumour necrosis factor antagonists in inflammatory bowel disease. Clin Gastroenterol Hepatol2012;10:1079–87.

Martelli L, Olivera P, Roblin X, et al. Cost-effectiveness of drug monitoring of anti-TNF therapy in inflammatory bowel disease and rheumatoid arthritis: a systematic review. Gastroenterology2016;Sep 24.

No conflict of interest