Antibodies against C1q Are a Valuable Serological Marker for Identification of Systemic Lupus Erythematosus Patients with Active Lupus Nephritis

Table 4

Significant difference in levels of anti-C1q and anti-dsDNA antibodies and C3 and C4 in patients with SLE compared to those with non-SLE autoimmune diseases or healthy individuals.

Group ()	Anti-C1q		Anti-dsDNA		Complements C3 and C4 (mean ± SD)
	Positive; (%)	Concentration; (mean ± SD); (AU/mL)	Positive; (%)	Concentration; (mean ± SD); (IU/mL)	Low C3 and C4; (%)	C3; (μg/mL)	C4; (μg/mL)
SLE (95)	50 (52.6)	106.8 ± 17.5	78 (82.1)	67.9 ± 20.2	61 (64.2)	0.57 ± 0.19	0.16 ± 0.08
Non-SLE (40)	3 (7.5)	15.7 ± 10.4	4 (10)	5.7 ± 1.6	3 (7.5)	1.25 ± 0.24	0.29 ± 0.08
Healthy (34)	1 (2.9)	8.5	2 (5.9)	4.8 ± 1.7	1 (2.9)	1.34	0.28

Non-SLE (): other autoimmune diseases include rheumatoid arthritis (RA) (5 cases), primary Sjögren’s syndrome (pSS) (10 cases), ankylosing spondylitis (AS) (2 cases), dermatomyositis (DM) (5 cases), Behçet’s disease (BD) (4 cases), systemic sclerosis (SSc) (3 cases), undifferentiated connective tissue disease (UCTD) (5 cases), and systemic vasculitis (3 cases). Compared to SLE group, ; C3 and C4 below normal range.