Development and validation of the AF score for diagnosis of adult-onset Still's disease in fever of unknown origin

•Persistent pruritic eruptions is a clinical feature of adult-onset Still’s disease (AOSD).•A weighted diagnostic score comprised 6 variables with fever as a prerequisite: persistent pruritic eruptions, evanescent rash, myalgia, neutrophil count, platelet count and serum ferritin. Score ≥5.245 is more likely to distinguish AOSD from fever of unknown.•The accuracy of the weighted score of AOSD was improved from 82.6% to 93.3% comparing with Yamaguchi's criteria.