Data quality and patient characteristics in European ANCA-associated vasculitis registries: data retrieval by federated querying

Data-driven subclassification of ANCA-associated vasculitis: model-based clustering of a federated international cohort

BACKGROUND

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis is a heterogenous autoimmune disease. While traditionally stratified into two conditions, granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), the subclassification of ANCA-associated vasculitis is subject to continued debate. Here we aim to identify phenotypically distinct subgroups and develop a data-driven subclassification of ANCA-associated vasculitis, using a large real-world dataset.

METHODS

In the collaborative data reuse project FAIRVASC (Findable, Accessible, Interoperable, Reusable, Vasculitis), registry records of patients with ANCA-associated vasculitis were retrieved from six European vasculitis registries: the Czech Registry of ANCA-associated vasculitis (Czech Republic), the French Vasculitis Study Group Registry (FVSG; France), the Joint Vasculitis Registry in German-speaking Countries (GeVas; Germany), the Polish Vasculitis Registry (POLVAS; Poland), the Irish Rare Kidney Disease Registry (RKD; Ireland), and the Skåne Vasculitis Cohort (Sweden). We performed model-based clustering of 17 mixed-type clinical variables using a parsimonious mixture of two latent Gaussian variable models. Clinical validation of the optimal cluster solution was made through summary statistics of the clusters' demography, phenotypic and serological characteristics, and outcome. The predictive value of models featuring the cluster affiliations were compared with classifications based on clinical diagnosis and ANCA specificity. People with lived experience were involved throughout the FAIRVASVC project.

FINDINGS

A total of 3868 patients diagnosed with ANCA-associated vasculitis between Nov 1, 1966, and March 1, 2023, were included in the study across the six registries (Czech Registry n=371, FVSG n=1780, GeVas n=135, POLVAS n=792, RKD n=439, and Skåne Vasculitis Cohort n=351). There were 2434 (62·9%) patients with GPA and 1434 (37·1%) with MPA. Mean age at diagnosis was 57·2 years (SD 16·4); 2006 (51·9%) of 3867 patients were men and 1861 (48·1%) were women. We identified five clusters, with distinct phenotype, biochemical presentation, and disease outcome. Three clusters were characterised by kidney involvement: one severe kidney cluster (555 [14·3%] of 3868 patients) with high C-reactive protein (CRP) and serum creatinine concentrations, and variable ANCA specificity (SK cluster); one myeloperoxidase (MPO)-ANCA-positive kidney involvement cluster (782 [20·2%]) with limited extrarenal disease (MPO-K cluster); and one proteinase 3 (PR3)-ANCA-positive kidney involvement cluster (683 [17·7%]) with widespread extrarenal disease (PR3-K cluster). Two clusters were characterised by relative absence of kidney involvement: one was a predominantly PR3-ANCA-positive cluster (1202 [31·1%]) with inflammatory multisystem disease (IMS cluster), and one was a cluster (646 [16·7%]) with predominantly ear-nose-throat involvement and low CRP, with mainly younger patients (YR cluster). Compared with models fitted with clinical diagnosis or ANCA status, cluster-assigned models demonstrated improved predictive power with respect to both patient and kidney survival.

INTERPRETATION

Our study reinforces the view that ANCA-associated vasculitis is not merely a binary construct. Data-driven subclassification of ANCA-associated vasculitis exhibits higher predictive value than current approaches for key outcomes.

FUNDING

European Union's Horizon 2020 research and innovation programme under the European Joint Programme on Rare Diseases.

Trends in health care of patients with vasculitides, including giant cell arteritis, Takayasu arteritis, ANCA-associated vasculitis and Behçet's disease: cross-sectional data of the German National Database 2007-2021

The aim of this study is to present the current care situation of patients with giant cell arteritis (GCA), Takayasu arteritis (TAK), ANCA-associated vasculitis (AAV) and Behçet's disease (BD). Trends over the last 15 years will reflect improvements and remaining deficits in the management of vasculitides. Consecutive cross-sectional data from patients with vasculitides from the German National Database (NDB) of the Collaborative Arthritis Centres between 2007 and 2021 were included. Medication, physician- and patient-reported outcomes on disease activity and disease burden, inpatient stays and occupational participation are compared for different vasculitis entities and over time. Employment rates were compared to German population rates. Between 502 and 854 vasculitis patients were annually documented. GCA and AAV were the most common vasculitides. Median disease duration ranged from 2 to 16 years. Over the years, glucocorticoids decreased in proportion and dose, most markedly in GCA and TAK, while biologic therapies increased up to 27%. Physicians rated disease activity as low for the vast majority of patients, while patients-reported moderate outcomes in many dimensions. PROs remained largely unchanged. The proportion of employed patients (< 65 years) increased from 47 to 57%. In recent years, biologics are increasingly used in patients with vasculitides, while glucocorticoids decreased significantly. PRO's have not improved. Work participation increased but remains lower than that in the German population.