Hospital Burden and Care Pathways of ANCA-Associated Vasculitis in Italy: A Focus on Clinical, Economic, and Geographic Dimensions

BACKGROUND: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) are rare autoimmune diseases characterized by heterogeneous clinical presentation and substantial morbidity. Evidence suggests high healthcare utilization and economic burden of ANCA-associated vasculitis (AAV), particularly owing to hospitalization as well as geographic variation in the organization of specialized care. However, national-level analyses examining outcomes, resource use, and geographic differences in care pathways remain limited. OBJECTIVE: The study aimed to identify hospitalized patients with granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) using administrative data, characterize their hospital burden and geographic care pathways in Italy, and investigate determinants of hospital costs and in-hospital mortality. METHODS: Nationwide Italian hospital discharge records (2010-2019) were used to identify patients with GPA and MPA using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM)-based algorithms. Hospital resource use, costs, in-hospital mortality, inter-regional mobility, and continuity of specialized care were estimated. Determinants of hospital costs were analyzed using generalized linear models (gamma distribution and log link), and in-hospital mortality was analyzed using the Cox proportional hazards model. RESULTS: We identified 3763 patients with GPA and 1206 patients with MPA, with a mean of 6.9 and 8.6 admissions per patient, respectively, over 10 years. In-hospital mortality was 20.3% (GPA) and 21.4% (MPA), with over 70% of deaths occurring within 2 years of the first observed key diagnosis in hospital records. Mean cumulative observed hospital costs during 2010-2019 were substantial (€28,275 for GPA and €36,462 for MPA per patient), with around 60% of costs concentrated in the year of the first observed key diagnosis and adjacent years. Marked regional variation in care pathways was observed, with patients residing in southern regions frequently receiving AAV-related care in northern hospitals. Lower hospital loyalty (seeking AAV-related care in numerous hospitals) was more commonly observed in several southern regions. In regression analyses, infections were the strongest predictors of both higher costs and in-hospital mortality, while lower hospital loyalty was associated with substantially higher costs but not in-hospital mortality. CONCLUSIONS: Our analysis showed that hospitalized patients with AAV in Italy experienced substantial inpatient burden, frequent admissions, and high in-hospital mortality. Infections and renal involvement were strongly associated with both costs and in-hospital mortality. The observed regional differences in mobility patterns and continuity of specialized care suggest important geographic variation in AAV care pathways within the Italian hospital system. These findings may help inform efforts to improve the coordination and continuity of specialized AAV care.