Methods: Patients with vasculitis or comparator diseases were recruited into an international cohort. The study proceeded in five phases: i) Identification of candidate items using consensus methodology; ii) Prospective data collection of candidate items present at the time of diagnosis; iii) Data-driven reduction of candidate items; iv) Expert panel review of cases to define the reference diagnosis; v) Derivation of a points-based risk score for disease classification in a development set using lasso logistic regression with subsequent validation of performance characteristics in an independent set of cases and comparators.
Results: The development set for MPA consisted of 149 cases of MPA and 409 comparators. The validation set consisted of an additional 142 cases of MPA and 414 comparators. From 91 candidate items, regression analysis identified 10 items for MPA, 6 of which were retained. The weighting of final criteria items was: i) pANCA or anti-MPO ANCA positivity (+6), ii) Pauci-immune glomerulonephritis (+3), iii) Lung fibrosis or interstitial lung disease (+3), iv) Sino-nasal symptoms or signs (-3), v) cANCA or anti-PR3 ANCA positivity (-1), and vi) Eosinophil count ≥ 1x109/L (-4). After excluding mimics of vasculitis, a patient with a diagnosis of small- or medium-vessel vasculitis could be classified as MPA with a cumulative score of ≥ 5 points. When these criteria were tested in the validation dataset, the sensitivity was 91% (95% confidence interval [95% CI] 85-95%) and the specificity was 94% (95% CI 92-96%).
Conclusion: The 2020 ACR-EULAR MPA Classification Criteria are now validated for use in clinical research.
Bibliographical noteFunding Information:
The Diagnostic and Classification Criteria in Vasculitis (DCVAS) study, of which the development of these classification criteria was a part, was funded by grants from the American College of Rheumatology (ACR), the European Alliance of Associations for Rheumatology (EULAR), the Vasculitis Foundation and the University of Pennsylvania Vasculitis Center.
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