Koyama K, et al. - In this retrospective, observational study, researchers focused on two subtypes of acute respiratory distress syndrome (ARDS) to identify biomarker profiles of coagulopathy and alveolar epithelial injury. These two subtypes included patients with direct common risk factors (dARDS) and those with idiopathic or immune-related diseases (iARDS), which are categorized as “ARDS without common risk factors” according to the Berlin definition. The presence of coagulopathy and alveolar epithelial injury was evident in both patients with dARDS and with iARDS. However, the two groups had significantly different biomarker profiles. For distinguishing these two subtypes, varied patterns of PAI-1 (plasminogen activator inhibitor-1), protein C (PC) activity, surfactant protein [SP]-D, and KL-6 may be helpful. An increase in thrombin–antithrombin complex [TAT] (marker of thrombin generation) and PAI-1 (marker of inhibited fibrinolysis), and above normal PC activity were seen in the iARDS patients, whereas a significant decline in PC activity and the presence of TAT or PAI-1 at much higher levels were seen in dARDS vs iARDS patients.