Histopathological characteristics overall and stratified by C9 staining groups
| Overall sample n=30 | Tubular C9 positive (stain intensity 1–3) n=7 | Tubular C9 negative (stain intensity) n=23 | P value | |
| Light microscopy | ||||
| IFTA*, n (%) | 0.009 | |||
| Minimal to mild (<25%) | 27 (90%) | 4 (57%) | 23 (100%) | |
| Moderate (25%–50%) | 3 (10%) | 3 (43%) | 0 (0%) | |
| Moderate NIH Chronicity Index*, n (%) | 5 (17%) | 3 (43%) | 2 (9%) | 0.07 |
| Pure/Mixed Proliferative LN class (3, 4, 3+5, 4+5), n (%) | 23 (77%) | 6 (86%) | 17 (74%) | >0.99 |
| Moderate NIH Activity Index†, n (%) | 12 (40%) | 2 (29%) | 10 (44%) | 0.67 |
| >10% glomeruli with sclerosis, n (%) | 10 (33%) | 5 (71%) | 5 (22%) | 0.03 |
| At least one crescent, n (%) | 14 (47%) | 4 (57%) | 10 (43%) | 0.68 |
| Complement glomerular IF microscopy | ||||
| C3 (score >1), n (%) | 29 (97%) | 7 (100%) | 22 (96%) | >0.99 |
| C4 (score >1), n (%) | 18 (60%) | 6 (86%) | 12 (52%) | 0.19 |
| C1q (score >1), n (%) | 30 (100%) | 7 (100%) | 23 (100%) | >0.99 |
| Classical complement pathway activation (C3+, C4+, C1q+), n (%) | 18 (60%) | 6 (86%) | 12 (52%) | 0.19 |
| C9 deposition, non-tubular | ||||
| Glomerular (score >0), n (%) | 13 (43%) | 3 (43%) | 10 (44%) | >0.99 |
| Arterioles/arteries (score >0), n (%) | 27 (90%) | 7 (100%) | 20 (87%) | >0.99 |
*Score 4–7.
†Score 6–14.
IF, immunofluorescence; IFTA, interstitial fibrosis/tubular atrophy.