The estimated best cut-off point for PTX3 between active SLE patients and healthy subjects was 2.8 ng/mL, characterized by a high sensitivity (100%) and high specificity (80%), with a negative predictive value of 1 (100%), positive predictive value of 0.76 (76%), and an accuracy of 0.88 (88%). The gene discussed is PTX3; the disease is systemic lupus erythematosus.