S100A9 and systemic lupus erythematosus: Although the level of protein S100-A9 (S100A9), alpha-1-acid glycoprotein 2 (ORM2), alpha-1-antitrypsin (SERPINA1) was altered in various diseases other than SLE, these proteins were selected for the candidate biomarker because of the establishing contrast level in serum/plasma between SLE patients and other related diseases, i.e., the level of alpha-1-antitrypsin (SERPINA1) was found to increase in SLE, but diminish in other systemic autoimmune diseases and liver diseases.