C4A and systemic lupus erythematosus: In this second validation cohort, four of the eight urine proteins interrogated, including ALCAM (AUC = 0.93), VCAM-1 (AUC = 0.92), TFPI (AUC = 0.88), and PF-4 (AUC = 0.83), outperformed C3/C4 and anti-dsDNA in discriminating active LN from inactive SLE, with improved AUC values and statistical significance, as detailed in Table 5 and Fig. 3b.