#5894 HYPOCOMPLEMENTEMIA AT DIAGNOSIS OF ANCA-ASSOCIATED VASCULITIS IS ASSOCIATED WITH SEVERITY AND OUTCOMES

Abstract

Abstract Background and Aims A relationship between antineutrophilic cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and complement has been shown, and complement has an important role in the pathogenesis of AAV [1]. Low serum complement levels (sC3) at diagnosis of AAV has been previously described although clinical characteristics and outcomes of AAV with hypocomplementemia still remain unclear [2]. The aim of this study was to investigate what proportion of patients with AAV have low sC3 at diagnosis, and whether they have different clinical and histological features or experience different outcomes compared to patients with normal sC3. Method A total of 93 patients with AAV diagnose (81,3% Anti-MPO and 18,7% anti-PR3) were included in the study from 2000-2022. 12% of them had sC3 values below limit of normal range (i.e., <90 mg/dl). Patients were categorized according to sC3 levels into 2 groups, hypocomplementemic (G1; mean C3: 73.1mg/dl), and normocomplementemic (G2; mean C3: 128.3mg/dl). Histological patterns were based on the Berden score and correlated with clinical features. Main outcomes of interest included severity of acute kidney injury at diagnose (AKI), histopathological patterns, end-stage kidney disease (ESKD) and death in the long term. Results No differences were identified in terms of demographics (age, gender, induction treatment). sC3 levels and serum creatinine were statistically associated (r2:-0.40; p<0.001). Patients with low sC3 had more severe renal involvement, at diagnose (G1: sCr 7.6mg/dl vs sCr 3.8mg/dl, p<0.001) without differences in ANCA levels and they were more likely to require acute dialysis around the initial diagnosis (p < 0.01). There were significant differences in sCr levels at diagnose (p<0.001) related to Berden score without differences in sC3 levels (Focal, n = 8 (8.6%), sCr 2.5 mg/dl, sC3 121.1 mg/dl; Crescentic, n = 23 (24.7%), sCr 6.41mg/dl, sC3 119.3 mg/dl; Mixed n = 16 (17.2%), sCr 3.6mg/dl, sC3 118.5 mg/dl; Sclerotic, n = 14 (15.1%) sCr 3.0 C3 129.1mg/dl). 55.5% of G1 patients deceased compared to 28% of G2. Lower sC3 levels (G1) were associated with mortality (log-rank 4.1; p<0.05) and composite outcome of ESKD or death (log-rank 5.9; p<0.05) compared G2 patients. Conclusion Hypocomplementemia in AAV at the disease onset was a risk factor for the serious organ damage, and a life prognostic factor. Low C3 levels at diagnosis of AAV is emerging as a predictor of renal outcomes and it is thus very important to pay attention to them. Despite that histologic patterns of the Berden classification were related to the severity of AKI at presentation there was no statistical correlation with sC3 levels. We recommend to pay attention to the levels of complement at the diagnosis of AAV.