Given the favorable response to JAKi observed in some patients with AOSD, we examined the role of type I IFN in disease pathogenesis using a novel assay to measure serum levels of several IFN‐responsive chemokines, CCL2, CCL8, CCL19, CXCL10, and CXCL11, and combined these levels into a serological IFN score. The gene discussed is CXCL11; the disease is adult-onset Still disease.