Plasma HMGB1 levels were not correlated to disease severity as defined by PSI risk class (Fig. 2B), and plasma HMGB1 levels were similar in patients with and without severe pneumonia according to the ATS/IDSA criteria, 44 ng/mL (range 20–173 ng/mL) vs. 59 ng/mL (range 6–320 ng/mL), p = 0.86, and in patients with and without sepsis, according to the Sepsis-3 criteria26, 58 ng/mL (range 6–320 ng/mL) vs. 59 ng/mL (range 6–320 ng/mL), p = 0.42. Here, HMGB1 is linked to susceptibility to pneumonia measurement.