Descriptive statistics (median, lower and upper quartile) at baseline by dichotomised entry diagnosis microscopic polyangiitis (MPA) and Wegener's granulomatosis (WG)
| N (n) | MPA (N=254) | WG (N=281) | Combined (N=535) | Test statistic p value | |
|---|---|---|---|---|---|
| Sex | 535 | ||||
| Male | 52% (133) | 55% (155) | 54% (288) | 0.521 | |
| Female | 48% (121) | 45% (126) | 46% (247) | ||
| Age years | 535 | 54 64 70 | 43 58 66 | 49 61 69 | <0.0012 |
| Entry age quartile | <0.0011 | ||||
| <50 years | 19% (48) | 33% (93) | 26% (141) | ||
| 50–60 years | 18% (46) | 24% (67) | 21% (113) | ||
| 60–70 years | 37% (94) | 27% (76) | 32% (170) | ||
| >70 years | 26% (66) | 16% (45) | 21% (111) | ||
| Serum creatinine µmol/l | 535 (523) | 174 335 654 | 82 107 292 | 97 203 498 | <0.0012 |
| GFR ml/min | 535 | 7.2 14.7 31.8 | 18.8 59.2 79.6 | 9.6 27.9 64.7 | <0.0012 |
| GFR categorised as CKD stage | 535 | <0.0011 | |||
| 1 | 2% (4) | 15% (41) | 8% (45) | ||
| 2 | 5% (13) | 34% (95) | 20% (108) | ||
| 3 | 20% (51) | 17% (49) | 19% (100) | ||
| 4 | 23% (58) | 14% (38) | 18% (96) | ||
| 5 | 50% (128) | 21% (58) | 35% (186) | ||
| CKD stage trichotomised | 535 | <0.0011 | |||
| A | 7% (17) | 48% (136) | 29% (153) | ||
| B | 43% (109) | 31% (87) | 37% (196) | ||
| C | 50% (128) | 21% (58) | 35% (186) | ||
| Haemoglobin g/dl | 535 (502) | 8.6 9.4 10.7 | 8.7 10.2 11.9 | 8.6 9.8 11.5 | <0.0012 |
| WBC 109/l | 535 (502) | 8.1 10.4 13.1 | 8.8 11.1 14.3 | 8.4 10.8 13.7 | <0.0212 |
| Platelets 109/l | 535 (501) | 254 330 436 | 301 400 534 | 276 364 482 | <0.0012 |
| CRP mg/l | 535 (485) | 13 41 98 | 21 65 142 | 18 54 118 | <0.0012 |
| ANCA ELISA only | 535 | <0.0011 | |||
| MPO | 58% (148) | 9% (26) | 33% (174) | ||
| PR3 | 25% (64) | 79% (222) | 53% (286) | ||
| Double positive; MPO and PR3 | 2% (4) | 4% (12) | 3% (16) | ||
| Negative | 13% (32) | 7% (19) | 10% (51) | ||
| Missing | 2% (6) | 1% (2) | 1% (8) | ||
| ANCA ELISA or IIF | 535 | <0.0011 | |||
| MPO | 67% (169) | 13% (36) | 38% (205) | ||
| PR3 | 26% (65) | 79% (223) | 54% (288) | ||
| Double positive; MPO and PR3 | 2% (4) | 4% (12) | 3% (16) | ||
| Negative | 4% (10) | 3% (8) | 3% (18) | ||
| Missing | 2% (6) | 1% (2) | 1% (8) | ||
| BVAS | 535 (504) | 13 15 21 | 12 20 26 | 12 17 23 | <0.0012 |
| BVAS quartiles | <0.0011 | ||||
| <10 | 11% (28) | 15% (42) | 13% (70) | ||
| 10–18 | 53% (134) | 23% (64) | 37% (198) | ||
| 18–23 | 18% (46) | 24% (67) | 21% (113) | ||
| >23 | 18% (46) | 38% (108) | 29% (154) |
N observations after single imputation (n) observations before single imputation test statistic used1Pearson test,2Wilcoxon test.
ANCA, antineutrophil cytoplasmic antibodies; BVAS, Birmingham Vasculitis Activity Score; CKD, chronic kidney disease; CRP, C-reactive protein; GFR, glomerular filtration rate; IIF, immunofluorescence microscopy; MPA, microscopic polyangiitis; MPO, myeloperoxidase; PR3, proteinase 3; WBC, white blood cell count; WG, Wegener's disease.