MO269INCREASED RISK OF DEATH IN PATIENTS WITH DOUBLE POSITIVE SEROLOGY OF ANTI-GLOMERULAR BASE MEMBRANE (ANTI-GBM) ANTIBODIES AND ANTI-NEUTROPHIL CYTOPLASMIC ANTIBODIES (ANCA)

Abstract Background and Aims Double positivity of anti-GBM ANCA serology is uncommon but may represent a distinct disease entity small vessel vasculitis. Previous research has been challenged by low incidence, conflicting results pertaining to risk death ESRD. Accordingly, we examined incidence outcomes based on data from multiple Danish nationwide healthcare registries. Method All patients with incident positive between 2013 2018 were identified 3 4 administrative regions in Denmark. Serological was defined as serum concentrations exceeding the upper reference level. either presence PR3-ANCA or MPO-ANCA within margin 30 days inclusion. Baseline information clinical diagnoses subsequently ascertained cross-referencing Risks ESRD compared adjusted absolute ratios (ARR) cumulative incidences assessed Aalen-Johansen estimator. Results A total 118 (4.4 cases/million/year) identified. Concomitant tested 104 (88.1%), 39 (37.5%) demonstrating double (20 13 for (51.3%) (33.3%), respectively, 6 all autoantibodies (5.8%)). Mean follow-up study population 1.9 (SD ±1.6) years. Compared alone, associated female gender (61.5%, P=0.02), more frequent employment plasma exchange (53.8%, P=0.04). No difference observed regard age (63.2 years [SD 18.5], P=0.60), mean concentration (125.5 182.4] IU/L vs. 108.9 212.7] IU/L, P=0.30). One-year mortality 17.7% (n=14) 28.2% (n=11) both ANCA. increased (ARR 2.10 [CI 1.20-3.65], P=0.009) (figure); however, there no 1.28 [0.66-2.50], P=0.46). Of patients, only 32 (27%) diagnosed according ICD10 code (1.2 cases/million/year). In confirmatory ICD-10 code, (40%) had (46.2% 53.8% MPO-ANCA). subset male (63.2%, P=0.07), numerical lower (56.1 25.2], P=0.50), (333.3 278.7] vs 150.7 146.5] P= 0.026). There two groups. Conclusion plausibly defines group higher death. While association an ICD10-confirmed diagnosis well established, significance alone remains uncertain.