Table 2 Comparison of clinical, laboratory and demographic variables in patients with a low or high interferon (IFN)-regulated gene signature
VariableIFN gene signature categoryp Value
Low IFN gene signature group (n = 119)High IFN gene signature group (n = 150)
Demographics:
    Age, years49.32 (13.34)40.74 (12.84)<0.001
    Sex (female/male)104/15137/13NS
    Race (Caucasian/African–American/Asian/other)92/13/8/6102/19/21/8NS
    Disease duration, years17.95 (10.27)14.55 (9.20)0.006
Disease activity markers:
    SLEDAI-2K score3.47 (4.10)5.11 (4.15)<0.001
    Increased anti-dsDNA antibody28 (23.53%)76 (50.67%)<0.001
    Low complement*34 (28.57%)84 (56.00%)<0.001
    Anti-dsDNA titre, U/ml7.96 (15.12)20.37 (29.91)<0.001
    C3, g/litre1.05 (0.24)0.90 (0.23)<0.001
    C4, g/litre0.21 (0.08)0.18 (0.09)<0.001
    CRP, mg/litre†6.27 (14.30)3.62 (7.40)0.022
    White blood cell count, 109/litre6.84 (2.77)5.73 (2.14)0.003
    Neutrophil count, 109/litre4.85 (2.63)4.17 (2.12)0.03
    Lymphocyte count, 109/litre1.41 (0.66)1.10 (0.58)<0.001
Clinical manifestations:
    Musculoskeletal10 (8.40%)23 (15.33%)NS
    Cutaneous26 (21.85%)48 (32.00%)NS
    Renal17 (14.29%)28 (5.33%)NS
    Neurological7 (5.88%)5 (3.33%)NS
    Serosal2 (1.68%)1 (0.67%)NS
    Haematological11 (9.24%)9 (6.0%)NS
    Immunological51 (42.86%)105 (70.00%)<0.001
    Vasculitis1 (0.84%)4 (2.67%)NS
    Fever3 (2.52%)2 (1.33%)NS
Autoantibody profile:‡
    Anti-Ro75 (63.03%)95 (63.33%)NS
    Anti-La44 (36.97%)62 (41.33%)NS
    Anti-Sm46 (38.66%)64 (42.67%)NS
    Anti-U1 RNP50 (42.02%)86 (57.33%)0.014
    Anti-RBP¶91 (76.47%)129 (86.00%)0.056
    Anti-phospholipid antibody58 (48.74%)63 (42.0%)NS
Medications:
    Prednisone59 (37.58%)98 (62.42%)0.013
    Prednisone dose, mg/day10.01 (8.05)10.49 (7.36)NS
    Antimalarials§80 (44.94%)98 (55.06%)NS
    Immunosuppressive therapy**49 (41.88%)68 (58.12%)NS
SDI1.97 (2.09)1.48 (1.78)0.034
  • Values are mean (SD) or number (%) of patients. Except for autoantibody profile‡, all values relate to the time of the study.

  • *Low C3 and/or low C4. †Based on 116 samples in the low IFN-regulated gene signature group and 142 samples in the high IFN-regulated gene signature group. ‡Ever present since diagnosis of SLE. ¶Antibodies to one or more RNA binding proteins. Comprises antibodies to Ro, La, Sm and U1 RNP. §Includes chloroquine and hydroxychloroquine. **Includes methotrexate, azathioprine, mycophenolate mofetil, ciclosporine and cyclophosphamide.

  • CRP, C-reactive protein; RBP, RNA binding protein; SDI, Systemic Lupus International Collaborative Clinics/American College of Rheumatology (SLICC/ACR) Damage Index; SLE, systemic lupus erythaematosus; SLEDAI-2K, SLE Disease Activity Index 2000.