Correlation analysis between IFIT4 expression and clinical assessments in SLE patients. Total RNA from the peripheral blood mononuclear cells (PBMCs) of 108 systemic lupus erythematosus (SLE) patients and 46 healthy donors (HDs) was isolated, and the relative expression levels of IFIT4 mRNA were determined using real-time quantitative RT-PCR. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was coamplified as an internal control to normalize the amount of RNA. In the total SLE population, the relative expression of IFIT4 was plotted against the following: (a) the titre of antinuclear antibody (ANA) in a group of 108 SLE patients; (b) the titre of anti-double-stranded DNA antibody (anti-dsDNA) in 36 SLE patients; and (c) the titre of anti-Smith antibody (anti-Sm) in 7 SLE patients. Spearman's correlation test was used to analyze these data. In the SLE population as a whole, the relative expression of IFIT4 was determined using real-time quantitative RT-PCR in patients who were positive or negative for the following: (d) anti-dsDNA antibody; (e) anti-SSA antibody; (f) anti-cardiolipid antibody or β-GP1 (ACL/b-GP1); (g) hypocomplementaemia (C3/C4 decrease); (h) haematocytopenia (wbc/PLT decrease); and (i) lupus nephritis. Mann-Whitney test was used to analyze these data. (j) The relative expression of IFIT4 was plotted against Systemic Lupus Erythematosus Disease Activity Index-2,000 (SLEDAI-2000) and analyzed usingy Spearman's test. IFIT4, interferon-induced protein with tetratricopeptide repeats 4.