Dose Reduction of Tumor Necrosis Factor Inhibitor and its Effect on Medical Costs for Patients with Ankylosing Spondylitis.

TNFi dose reduction was identified in 17.8% of the patients with AS, and the patterns were different for each TNFi. Additionally, the dose reductions significantly reduced the medical costs associated with AS, that is, from 24.85 to 35.52% of the total medical expenditure.