280. Urinary IgA and C5a levels are indicators of renal involvement in children with IgA Vasculitis

Background: Nephritis is a recognised complication in children with IgA Vasculitis (IgAV, previously Henoch-Schönlein Purpura) and accounts for 1-2% of kidney failure. Understanding the pathophysiology of this disease may allow identification of targets for earlier diagnosis and/or treatment. The aim of this cross-sectional study was to assess whether Immunoglobulin A (IgA) and Complement 5a (C5a) could be detected in the urine of children with IgAV and whether they are increased in patients with nephritis. Methods: Paediatric patients and healthy controls (HC) were recruited as part of the IgA Vasculitis Study (Alder Hey Children’s NHS Foundation Trust, Liverpool, REC 17/NE/0390). Urinary IgA and C5a levels were measured using commercially available ELISA kits (Novus Biological) and normalised to creatinine. Patients were grouped into IgAV nephritis (IgAVN) or IgAV with no nephritis (IgAVwoN). Nephritis was defined as a urinary albumin-creatinine ratio (UACR) > 30 mg/mmol at the time of sample collection. Statistical analysis was performed using GraphPad Prism version 8.0. Data is presented as median [range]. Results: A total of 59 children were included in this study (IgAVN n=11, IgAVwoN n=36, HC n=12). Median age was 7.1 years [1.8-17.9] and male to female ratio was 1.9:1. Urinary IgA and urinary C5a levels were both increased in patients with IgAVN (IgA/Cr –2504.5 ug/g [483.0-12437.7]; C5a/Cr – 720.2 ng/g [157.6-7826.3]) compared to IgAVwoN (IgA/Cr – 535.7 ug/g [4.4-8035.5]; C5a/Cr – 121.5 ng/g [9.03-2214.8]; p < 0.01) and HC (IgA/Cr – 430.6 ug/g [166.4-1168.6]; C5a/Cr – 55.1 ng/g [15.2-1138.9]: p < 0.01). There was no difference between HC and IgAVwoN. There were clear outliers with extremely increased urinary IgA and C5a levels in both IgAVN and IgAVwoN groups (Figure 1). Conclusion: Urinary IgA and C5a can be measured and the concentration appeared to be associated with nephritis in this cohort. These could be useful markers to identify patients who warrant further intervention and/or potential drug targets. Further longitudinal studies are needed to assess their clinical relevance. Disclosures: None