Receiver operating characteristic curves (ROC) for the metabolites between the systemic inflammatory response syndrome (n=15) and sepsis (n=35) groups (A); the sepsis (n=10) and severe sepsis (n=25) groups (B); the sepsis (n=26) and death (n=9) groups (C). Receiver operating characteristic curves (ROC) for the metabolites between the systemic inflammatory response syndrome (n=15) and sepsis (n=35) groups (A); the sepsis (n=10) and severe sepsis (n=25) groups (B); the sepsis (n=26) and death (n=9) groups (C). AUC indicates the area under the curve. Longxiang Su et al. BMJ Open Resp Res 2014;1:e000056 ©2014 by British Thoracic Society