Improving pharmacoeconomic evidence of therapeutic drug monitoring for chronic inflammatory diseases across Europe

This manuscript aims to present the authors’ position on the current evidence and identify key gaps in the pharmacoeconomic evaluation of therapeutic drug monitoring (TDM) for chronic inflammatory diseases (CIDs) across Europe. Specifically, it will address: (i) the clinical effectiveness and safety of TDM for pharmacoeconomic evaluation; (ii) available comparative analyses of TDM and their potential use in economic analyses; (iii) existing cost-effectiveness analyses (CEAs) of TDM; and (iv) budget impact analyses. By synthesizing these dimensions, the manuscript seeks to provide a foundation for more consistent, transparent, and policy-relevant economic evidence to support the implementation of TDM within European healthcare systems. TDM can guide dose adjustment, continuation or discontinuation, changes to concomitant therapy, and next-line selection. To rationalize the use of high-cost biologics and improve access in low- and middle-income countries, TDM is policy-relevant, yet published CEAs are largely limited to older TNF-α inhibitors (mainly infliximab and adalimumab) and high-income settings. Available CEAs have also applied TDM inconsistently and assumed various direct effects, reflecting limited clinical certainty. Future work should standardize TDM algorithms, use comparative designs, include comprehensive costing, extend beyond TNF-α agents, and prioritize studies in low- and middle-income countries.