Fig. 3

Plasma C4d levels associate with lupus nephritis (LN) in the cross-sectional study and are convincing as an accurate marker for LN. a At higher disease activity (DA), plasma C4d levels are elevated in patients with LN (n = 34) compared with patients without LN (n = 64). Data are presented as medians with 25–75% quantiles plus whiskers, and significance was calculated using the Mann-Whitney U test. b Area under the ROC curve analysis showing accuracy of C4d, C3, and C4 as markers for LN. c Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for C4d, C3, and C4 as markers for LN. Data are presented with 95% CIs. d Association of high C4d (>0.42 mg/L), low C3 (<0.77 g/L), and low C4 (<0.12 g/L) levels alone as well as in combination with the presence of anti-double-stranded DNA antibodies with LN. Significance was calculated using binary logistics, and ORs are indicated with a dot connected to the 95% CI. Significant ORs are shown in bold and marked in red