Balanced inpatient and outpatient reimbursement versus hospitalization-favored insurance reduces Crohn disease costs and improves biologic drug persistence: A mediation analysis

Crohn disease (CD) treatment incurs high costs due to biologics and frequent hospitalizations. Insurance policies favoring hospitalization may increase costs by discouraging outpatient care. We conducted a mediation analysis to examine whether balanced inpatient and outpatient reimbursement reduces CD treatment costs and improves biologic persistence, mediated by outpatient treatment. In this retrospective cohort study, we analyzed 133 CD patients initiating ustekinumab (UST) in 2022 at a tertiary hospital. The exposure was balanced insurance coverage (Hangzhou Medical Insurance) versus hospitalization-favored coverage (Zhejiang Province Card Insurance). The mediator was outpatient UST treatment. Primary outcome was total CD-related treatment costs; secondary outcomes included CD-related inpatient stays, outpatient visits, and UST persistence. Causal mediation analysis, adjusted for age, gender, and disease severity, estimated natural direct effects, natural indirect effects (NIE), and proportion mediated. Patients with balanced coverage had lower total CD-related costs (adjusted mean difference: -CNY 6362; 95% CI: -11,658 to - 1067), fully mediated by increased outpatient treatment (NIE: -CNY 10,125; 95% CI: -15,920 to - 4330; proportion mediated: 100%). They had fewer inpatient stays (-1.64; 95% CI: -2.10 to - 1.18; NIE: -0.84; 95% CI: -1.33 to - 0.37; proportion mediated: 50%) and more outpatient visits (6.53; 95% CI: 5.48 to 7.57). Balanced coverage reduced UST discontinuation risk by 73% (adjusted HR: 0.27; 95% CI: 0.10-0.74), not mediated by outpatient treatment. Balanced insurance coverage reduces CD treatment costs and inpatient stays via increased outpatient treatment and improves UST persistence independently. Policymakers should equalize coverage to optimize CD care efficiency.