PTX3 and systemic lupus erythematosus: Our study defined PTX3 plasma value in healthy subjects (2.3 ± 1.1 ng/mL) according to other studies, the concentration of PTX3 in SLE patients at different SLEDAI stage, and most importantly an operative cut-off (2.8 ng/mL), characterized by a high sensitivity (100%) and high specificity (80%).