Updated project metadata. In an endotoxaemic mouse model of sepsis, a tissue-based proteomics approach for biomarker discovery identified long pentraxin 3 (PTX3) as the lead candidate for inflamed myocardium. PTX3 accumulated as an octamer due to disulphide-bond formation in heart, kidney and lung ?common organ dysfunctions seen in patients with sepsis. Oligomeric moieties of PTX3 were also detectable in the circulation. The redox-state of PTX3 was quantified over the first 11 days in critically ill adult patients with sepsis. On admission day, there was no difference in the redox-state of PTX3 between survivors and non-survivors. From day 2 onwards, the conversion of octameric to monomeric PTX3 was consistently associated with a greater survival after 28 days of follow-up. For example, by day 2 post admission, octameric PTX3 was undetectable in survivors, but still constituted more than half of total PTX3 in non-survivors (P<0.001). Monomeric PTX3 was inversely associated with cardiac damage markers NT-proBNP, high sensitivity troponin I and T. In comparison to the conventional measurements of total PTX3 or NT-proBNP, the redox-sensitive oligomerization of PTX3 was more dynamic and a superior predictor of disease outcome.