HMGB1 and infectious disease: In the patients with FUO to diagnose infectious disease subtype, the most appropriate cut-off value for serum HMGB1 was 6.63 ng/mL with the sensitivity (42.3%), specificity (60.9%), and area under the curve (0.54); to diagnose autoimmune disease subtype, the most appropriate cut-off value for serum anti-HMGB1 antibodies was 9.81 RU/mL with the sensitivity (55%), specificity (88.2%), and area under the curve (0.70) (Fig. 1c,d).