Table 2. Comparison of clinical and biological features according to serum C3 levels.
| Low C3 group | High C3 group | P | |
|---|---|---|---|
| n = 22 | n = 23 | ||
| Baseline characteristics | |||
| Sex (M/F), n (%) | 11/11 | 15/8 | 0.302 |
| Age (years) | 67.2 ± 13.4 [28–83] | 61.0 ± 14.8 [18–77] | 0.150 |
| Weight (kg) | 70.9 ± 15.1 [51–102] | 73.9 ± 14.9 [50–107] | 0.526 |
| Hypertension, n (%) | 15 (68.2) | 9 (39.1) | 0.051 |
| Diabetes mellitus, n (%) | 3 (13.6) | 3 (13.0) | 1.000 |
| Biological characteristics | |||
| Complement component level, mg/dL | |||
| C3 level | 105.4 ± 11.1 [78–120] | 144.5 ± 19.2 [121–184] | <0.0001 |
| C4 level | 25.3 ± 7.3 [10–39] | 32.7 ± 10.2 [14–58] | 0.008 |
| Antinuclear antibodies (>1/200) | 7 (31.8) | 3 (13.0) | 0.129 |
| Serum albumin, g/L | 30.2 ± 7.0 [22–42] | 29.8 ± 6.3 [17–40] | 0.873 |
| C-reactive protein, mg/dL | 75.1 ± 55.6 [8–167] | 123.2 ± 96.0 [10–297] | 0.057 |
| Hemoglobin, g/dL | 9.8 ± 1.7 [7–12.2] | 9.2 ± 1.9 [5.7–11.1] | 0.393 |
| Lactate deshydrogenase (UI/L) | 384.0 ± 141 [151–693] | 269.5 ± 81 [143–459] | 0.013 |
| ANCA-associated vasculitis characteristics | |||
| Diagnosis, n (%) | |||
| GPA/MPA | 12 (54.5) / 10 (45.5) | 15 (65.2) / 8 (34.8) | 0.465 |
| c-ANCA / p-ANCA | 6 (27.2) / 16 (72.8) | 10 (43.5) / 13 (56.5) | 0.256 |
| PR3/MPO-ANCA | 7 (31.8) / 15 (68.2) | 10 (43.5) / 13 (56.5) | 0.420 |
| BVAS | 16.0 ± 4.7 [12–32] | 16.5 ± 4.1 [12–27] | 0.719 |
| Organ involvement, n (%) | |||
| Cutaneous signs | 4 (18.2) | 4 (17.4) | 1.000 |
| Ear, nose, throat | 7 (31.8) | 12 (52.2) | 0.167 |
| Heart | 1 (4.6) | 1 (4.3) | 1.000 |
| Digestive | 1 (4.5) | 2 (8.7) | 1.000 |
| Lung | 8 (36.4) | 9 (39.1) | 0.848 |
| Alveolar hemorrhage | 1 (4.5) | 2 (8.7) | 1.000 |
| Renal | 22 (100) | 22 (95.7) | 1.000 |
| Serum creatinine, μmol/L | 543.6 ± 491.5 [67–1906] | 235.0 ± 206.7 [49–700] | 0.008 |
| eGFR, mL/min/1.73 m2 | 20.1 ± 22.0 [2.2–96.6] | 48.6 ± 35.5 [5.4–115.4] | 0.002 |
| Proteinuria/creatininuria (g/g) | 4.3 ± 3.3 [1.2–16.0] | 2.5 ± 2.4 [0.2–9.7] | 0.059 |
| Renal replacement therapy at diagnosis, n (%) | 9 (40.9) | 5 (21.7) | 0.164 |
| Neurological | 1 (4.5) | 3 (13.0) | 1.000 |
| Immunosuppressive treatment | |||
| Steroids—Cyc | 15 (68.2) | 19 (82.6) | 0.314 |
| Steroids—PE—Cyc | 7 (31.8) | 4 (17.4) | 0.314 |
| Patient’s follow-up* (months) | 45.4 ± 47 [0.1–173] | 63.4 ± 50 [7.1–163] | 0.156 |
* until death or last visit.