Cluster Analysis To Explore Clinical Subphenotypes Of Eosinophilic Granulomatosis With Polyangiitis (Churg–Strauss)
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ObjectivePrevious studies suggested that distinct phenotypes of eosinophilic granulomatosis with polyangiitis (EGPA) could be determined by presence or absence of antineutrophil cytoplasmic antibodies (ANCA), reflecting predominant vasculitic or eosinophilic processes, respectively. This study explored whether ANCA-based clusters or other clusters can be identified in EGPA.MethodsThis study used standardized data of 15 European centers for patients with EGPA fulfilling widely accepted classification criteria. We used multiple correspondence analysis, hierarchical cluster analysis, and a decision tree model. The main model included 10 clinical variables (musculoskeletal, mucocutaneous, ophthalmological, ENT, cardiovascular, pulmonary, gastrointestinal, renal, central or peripheral neurological involvement); a second model also included ANCA results.ResultsThe analyses included 489 patients diagnosed in 1984–2015. ANCA were detected in 37.2% of patients, mostly P-ANCA (85.4%) and/or anti-myeloperoxidase (87.0%). Compared with ANCA-negative patients, those with ANCA had more renal (P<0.001) and peripheral neurological involvement (P=0.04), fewer cardiovascular signs (P<0.001) and fewer biopsies with eosinophilic tissue infiltrates (P=0.001). The cluster analyses generated four (model without ANCA) and five clusters (model with ANCA). Both models identified three identical clusters of 34, 39 and 40 patients according to the presence or absence of ENT, CNS and ophthalmological involvement. Peripheral neurological and cardiovascular involvement were not predictive characteristics.ConclusionAlthough reinforcing the known association of ANCA status with clinical manifestations, cluster analysis does not support a complete separation of EGPA in ANCA-positive and –negative subsets. Collectively, these data indicate that EGPA should be regarded as a phenotypic spectrum rather than a dichotomous disease.
