ResumeIntroductionWe previously reported that serum levels of endocan, an endothelial derived dermatan sulphate proteoglycan which regulates LFA-1/ ICAM-1 interactionsin vitro, are elevated in patients with sepsis. As the endothelium is an important player in sepsis, and endothelial activation parallel sepsis severity, we wonder if blood levels of endocan could be used as a diagnostic and prognostic marker in sepsis and how it compares with previously pro-posed markers as von Willebrand factor, IL6, IL 10, Procalcitonin or C reactive protein. We also studied kinetics of endocan secretion by endothelial cellsin vitroafter stimulation by soluble mediators involved in sepsis.Material and methodsEndocan values were quantified by an in house sandwich type ELISA. Commercial assays were used for procalcitonin, C reactive protein, IL10, IL6, von Willebrand Factor.DesignProspective observational study.SettingIntensive care unit (ICU) of the University Hospitals of Lille, France, and Geneva, Switzerland.PatientsAll patients admitted to the intensive care unit over a 6-month period with clinical evidence of sepsis.InterventionsNone.Measurements and main resultsIn vitro, we showed a sustained endocan secretion by endothelial cells after stimulation by LPS and TNFα. Circulating levels of endocan measured in 63 patients admitted in ICU with sepsis were significantly elevated compared to 20 healthy donors and 7 SIRS patients: 2.71 ± 4.88 ng/mlvs0.77 ± 0.44 ng/ml vs 0.68 ± 1.03 ng/ml (médian ± interquartile range) (p < 0.001). Endocan levels were higher in patients with septic shock (6.11 + 12.99 ng/ml, n = 22) than in patients with severe sepsis (1.97 ± 7.8 ng/ml, n= 12) or sepsis (1.95 ± 1.63 ng/ml, n = 29). Measurement of endocan at ICU admission revealed higher levels in non survivors (n = 12) than in patients still alive 10 days later (n = 51) (6.98+13.8 vs 2.45 + 4.09, p < 0.01) and was the only marker which had a prognostic significance.ConclusionsThese results suggest that in septic patients, endocan blood level is related to the severity and to the outcome of the patients, and may represent a novel endothelial cell dysfunction marker.