Table 1.
Demographic characteristics of the study participants*
| SLE | RA | Blood donors | |
|---|---|---|---|
| Patients included, no. | 206 | 199 | 513 |
| Female sex at birth | 188 (91.3) | 142 (71.4) | 252 (49.1) |
| Age, median (IQR) years | 49.0 (38.3–60.1) | 62.5 (51.6–70.5) | 47 (33–57) |
| BMI, median (IQR) kg/m2 | 24.2 (21.8–27.8) | 25.8 (22.5–28.9) | 25.5 (23.1–28.4) |
| Disease duration, median (IQR) years | 11.9 (6.0–24.0) | 14.0 (8.0–21.0) | – |
| Charlson Comorbidity Index, median (IQR) | 2 (1–3) | 3 (2–4) | – |
| Smoking | |||
| Active | 21 (11) | 26 (14) | – |
| Previous | 75 (38) | 95 (50) | – |
| Never | 100 (51) | 70 (37) | – |
| Hypertension | 53 (25.7) | 46 (23.4) | – |
| Caucasian | 198 (96.1) | 198 (99.5) | – |
| Rheumatoid arthritis | |||
| Anti‐CCP positivity | – | 146 of 196 (74.5) | – |
| IgM RF positivity | – | 137 (69) | – |
| Erosive disease on radiograph | – | 158 (79) | – |
| Systemic lupus erythematosus | |||
| ACR classification criteria | |||
| Malar rash | 129 (63) | – | – |
| Discoid rash | 133 (6) | – | – |
| Photosensitivity | 105 (51) | – | – |
| Oral ulcers | 61 (30) | – | – |
| Nonerosive arthritis | 172 (84) | – | – |
| Pleuritis or pericarditis | 61 (30) | – | – |
| Renal disorder | 60 (29) | – | – |
| Neurologic disorder | 14 (79) | – | – |
| Hematologic disorder | 151 (73) | – | – |
| Immunologic disorder, | 188 (91) | – | – |
| Positive antinuclear antibody | 204 (99) | – | – |
| SLICC score, median (IQR) | 1 (0–2) | – | – |
*
Values are the number (%) unless indicated otherwise. ACR = American College of Rheumatology; Anti‐CCP = anti–cyclic citrullinated peptide; BMI = body mass index; IQR = interquartile range; RA = rheumatoid arthritis; RF = rheumatoid factor; SLE = systemic lupus erythematosus; SLICC = Systemic Lupus International Collaborating Clinics.