medwireNews: An international group of experts has developed and validated classification criteria for eosinophilic granulomatosis with polyangiitis (EGPA), GPA, and microscopic polyangiitis (MPA).
“These criteria have been endorsed by the ACR [American College of Rheumatology] and EULAR and are now ready for use to differentiate one type of vasculitis from another to define populations in research studies,” write Peter Merkel (University of Pennsylvania, Philadelphia, USA) and colleagues.
They caution, however, that the criteria “are not appropriate for use in establishing a diagnosis of vasculitis” and “should only be applied when a diagnosis of small- or medium-vessel vasculitis has been made and all potential ‘vasculitis mimics’ have been excluded.”
As outlined in three articles published in the Annals of the Rheumatic Diseases, the criteria for each condition were developed and validated using data from the prospective DCVAS study. The patient numbers in the development datasets ranged from 107 to 578, while the comparator groups – involving people with other forms of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis and other small- and medium-vessel vasculitidies – included between 408 and 652 patients.
The classification criteria comprised seven items for EGPA, 10 for GPA, and six for MPA, and all incorporated ANCA testing. When these criteria were tested in the validation datasets, involving 119–146 cases and 161–437 comparators, they had “excellent sensitivity and specificity,” say the authors. Specifically, the sensitivity ranged from 84.9% for EGPA to 92.5% for GPA, while the specificity ranged from 93.8% for GPA to 99.1% for EGPA. Area under the receiver operating characteristic curve analysis demonstrated an accuracy of 99%, 99%, and 97% for the EGPA, GPA and MPA criteria, respectively.
Merkel and team note that the classification criteria for EGPA and GPA represent updates to previous iterations, whereas those for MPA are new.
They also point out that the criteria were produced using data from adults with vasculitis, and even though the clinical characteristics of the vasculitidies “are not known to differ substantially between adults and children, these criteria should be applied to children with some caution.”
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