IFNA1 and systemic lupus erythematosus: To validate the accuracy of serum IFN measurement by WISH bioassay, we have additionally measured serum IFNα2a protein by S-PLEX immunoassay (Meso Scale Discovery, USA), a recently developed highly sensitive electrochemiluminescence immunoassay which could measure cytokines to fg/ml levels [33], from some of SLE patients in this study.