Pneumonia and in-hospital mortality in ANCA-associated vasculitis: A nationwide population-based registry study in Spain

Abstract

[EN]To determine the incidence, predictors and impact of pneumonia among hospitalized patients with ANCA-associated vasculitis (AAV). A nationwide retrospective analysis of Spanish hospital discharges (2016-2023) identified all AAV admissions and coexisting pneumonia using ICD-10 codes. Outcomes included pneumonia incidence, intensive care unit (ICU) utilization, length of stay, temporal trends, in-hospital mortality and case fatality rate (CFR). Illness severity was classified using the severity of illness (SOI) and risk of mortality (ROM) indices. Multivariable logistic regression was used to identify independent predictors of in-hospital mortality. Among 12 378 AAV hospitalizations, 1280 (10.3%) had pneumonia. Pneumonia was associated with higher ICU admission rates (13.5% vs 6.5%), longer stays (median 22 vs 17 days), and greater in-hospital mortality (14.9% vs 4.4%) than those without pneumonia (all P < 0.001). In-hospital AAV mortality increased significantly over time (incidence rate ratio [IRR], 1.13 per year; P < 0.001). Viral pneumonia cases in AAV surged during the COVID-19 pandemic (2021-2022), declined by 2023, and showed a significant overall increase across the study period (IRR, 1.46; 95% CI: 1.38, 1.54; P < 0.001). In-hospital CFR rose sharply with extreme SOI (27.1% vs 18.7%; P < 0.001). Pneumonia was an independent predictor of death (odds ratio 1.97; 95% CI: 1.63, 2.37; P < 0.001), and a higher ROM was strongly associated with mortality risk. Around 1 in 10 hospitalizations with AAV develop pneumonia, which is associated with higher odds of in-hospital death and greater ICU utilization. Pneumonia is strongly associated with worse outcomes in AAV, supporting the need for proactive infection prevention and early treatment in AAV.