<h3>Background</h3> Differentiation of Systemic Lupus Erythematosus (SLE) activity and infection in a febrile SLE patient become difficult, since initial clinical presentation may be similar. Several biological markers (including procalcitonin and CRP) have been evaluated, with discordant results. Soluble CD14 (sCD14), also called presepsin, is the receptor for lipopolysaccharide - lipopolysaccharide binding protein (LPS-LBP) complexes. CD14 could activate a series of signal transduction pathways and inflammatory cascades, and lead to systemic inflammatory responses.(1) <h3>Objectives</h3> The aim of this study is to evaluate the utility of sCD14 as a biomarker to differentiate infection <i>vs.</i> activity in SLE patients admitted with systemic inflammatory response (SIRS). <h3>Methods</h3> We included 11 patients with SLE (ACR criteria 1997) and SIRS (International conference 2001) admitted to the ER and/or ICU. The measurement of sCD14 in plasma by enzymatic immunoassay of chemiluminescence <i>in vitro</i> was performed to differentiate active SLE <i>vs.</i> infection. Infection was considered if a positive culture/PCR was obtained. Mann-Whitney test was used to evaluate the association of variables with infection. <h3>Results</h3> All patients were female; mean age 37.9 years. An infectious disease was confirmed in 5 cases (3 bacterial including urinary tract infection, pneumonia and bacteremia; 1 viral infection by Chikungunya virus and 1 fungal by <i>histoplasma capsulatum</i>). sCD14 was elevated in the infected SLE patients (median: 1005 pg/mL- RIC: 533–1415-) vs patients with lupus flare (median: 431.5 pg/mL - RIC: 369–579-) (p=0,04). <h3>Conclusions</h3> High values of sCD14 levels seem to be useful to differentiate infections from activity in SLE patients with SIRS. More patients and further analysis are necessary to define the clinical use of this biomarker. <h3>References</h3> Zou Q, Wen W, Zhang X. Presepsin as a novel sepsis biomarker. World J Emerg Med [Internet]. Second Affiliated Hospital of Zhejiang University School of Medicine; 2014 Aug 22;5(1):16–9. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4129857. <h3>Disclosure of Interest</h3> None declared