Results of the univariate analysis of risk factors for a relapse from the time of an ANCA rise. Differences were assessed using the log-rank test for categorical variables and a Cox regression model for continuous variables.
| Univariate Analysis | Cox Regression | p | Log-rank | p | |
|---|---|---|---|---|---|
| HR | 95% CI | Chi-square | |||
| Age | 1.00 | 0.97–1.02 | 0.997 | — | — |
| Male | 1.12 | 0.55–2.22 | — | 0.084 | 0.772 |
| MPO-ANCA | 0.92 | 0.57–1.49 | — | 0.118 | 0.732 |
| ENT involvement | 0.62 | 0.28–1.36 | — | 1.546 | 0.214 |
| BVAS v3 | 0.96 | 0.91–1.01 | 0.122 | — | — |
| GPA | 0.98 | 0.29–3.35 | — | 0.001 | 0.977 |
| Therapy | |||||
| Induction regimen with CYC/RTX | 0.33 | 0.16–0.68 | — | 10.708 | 0.001 |
| Current immunosuppressive therapy | 1.66 | 0.64–4.30 | — | 1.173 | 0.279 |
| Antibiotic maintenance therapy | 0.99 | 0.83–1.18 | — | 0.010 | 0.922 |
| Followup | |||||
| Previously ANCA-negative | 1.21 | 0.85–1.73 | — | 1.158 | 0.282 |
| ANCA rise | |||||
| Time since previous disease activity, mos | 1.00 | 0.98–1.02 | 0.717 | — | — |
| Slope of the rise | 1.00 | 1.00–1.01 | 0.933 | — | — |
| ANCA value at rise | 1.00 | 1.00–1.00 | 0.903 | — | — |
| Concomitant IIF rise | 0.99 | 0.35–2.80 | — | 0.001 | 0.979 |
| Extended rise | 2.70 | 1.22–5.96 | — | 6.862 | 0.009 |
| Season | 12.383 | 0.006 | |||
| Spring | Reference | ||||
| Summer | 1.16 | 0.43–3.11 | — | ||
| Fall | 3.95 | 1.50–10.36 | — | ||
| Winter | 2.10 | 0.75–5.83 | — | ||
| 25-hydroxy Vitamin D | |||||
| Vitamin D, continuous variable | 1.01 | 0.99–1.03 | 0.377 | — | — |
| Hypovitaminosis D, ≤ 75 nmol/l | 1.39 | 0.33–5.84 | — | 0.215 | 0.643 |
Significant data are in bold face. ANCA: antineutrophil cytoplasmic antibodies; MPO-ANCA: myeloperoxidase ANCA; BVAS: Birmingham Vasculitis Activity Score; GPA: granulomatosis with polyangiitis; CYC: cyclophosphamide; RTX: rituximab; IIF: indirect immunofluorescence.