Abstract Background Hospitals in the southwest of the Netherlands collaborate to improve inflammatory bowel disease (IBD) care. As part of this initiative, a standardised care pathway (CP) for the treatment of IBD with biologics and small new molecules has been developed. The CP addresses initiation, switching, and discontinuation of therapy, as well as diagnostic testing and treatment follow-up. The CP has been implemented in six of the eight hospitals to improve patient outcomes, standardise care and reduce healthcare costs. This natural experiment provides an opportunity to evaluate the cost-effectiveness of the CP using a quasi-experimental design. We aimed to estimate the causal effect of CP implementation on costs and health outcomes. Methods A cost-utility analysis with a societal perspective was conducted. Adult patients with an IBD diagnosis for at least 3 months and treated with biologics and small new molecules were eligible for inclusion. Costs were assessed for both standard care (December 2020 - December 2021) and the CP over a one-year period (March 2022 – March 2023), without discounting costs and effects and standardizing costs to 2022. Missing data were handled using single imputation nested within a bootstrap procedure. The analysis employed a difference-in-differences (DiD) approach to estimate causal effects of the CP implementation, controlling for pre-existing differences between hospitals and general time trends that would have occurred without the intervention. For the cost-effectiveness analysis, we utilized the cumulative incremental costs and mean incremental quality adjusted life years (QALYs) from the post-intervention DiD effects. The DiD-derived incremental costs and QALYs were used to calculate the incremental cost-effectiveness ratio (ICER) and construct cost-effectiveness acceptability curves using normal approximation. Results Approximately 25% of the eligible population was included. At baseline, patients in intervention (n=842) and control hospitals (n=331) had comparable characteristics in terms of age, sex, diagnosis and comorbidities. The DiD-analysis showed cost savings primarily driven by reduced hospital costs (-€1,107; 95%CI: -€2,130 to -€109) while maintaining quality of life (QALY difference: 0.01; 95%CI: -0.02 to 0.04). The ICER was located in the southeast corner of the cost-effectiveness plane, indicating that the treatment with the CP is a dominant strategy compared to standard care (Figure 1). Conclusion A CP for the treatment of IBD with biologics and small new molecules was developed to improve IBD care and reduce healthcare costs. Our results showed that standardising IBD care is effective for reducing healthcare costs, while maintaining quality of life.
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