C3 and kidney disorder: Lastly, to test whether S100 urine and/or protein levels at baseline can predict clinical response to treatment escalation with RTX in patients with active LN, S100 proteins were included in binary logistic models either alone (crude) or adjusted for confounders such as age, disease duration, renal disease (outcome ‘active renal disease’), disease activity (outcome ‘higher disease’), low serum complement C3 and/or C4 (outcome ‘positive’), the presence or absence of anti-dsDNA antibodies (outcome ‘positive’) and corticosteroid dose.