AMSTERDAM – New classification criteria for antineutrophil cytoplasmic antibody (ANCA)–associated vasculitides have been drafted and now need formal review by the American College of Rheumatology and the European League Against Rheumatism before they can be put into practice.
Sara Freeman/MDedge News
Dr. Joanna Robson
According to Joanna Robson, MBBS, PhD, the chair of the DCVAS steering committee, these new criteria better “reflect current practice by incorporating, but not relying on, ANCA testing and advanced imaging.”
“The old criteria were actually produced in the early 1990s and since then we’ve had further thinking about the different subtypes of systemic vasculitis,” explained Dr. Robson of the University of the West of England in Bristol. There has also been a consensus conference held at Chapel Hill (Arthritis Rheum 2013;65[1]:1-11) which identified MPA as a separate entity, and ANCA testing has become routine practice. Computed tomography and magnetic resonance imaging are also now used to help differentiate between the different vasculitides.
“This really has been a collaborative, multinational effort,” Dr. Robson said at the European Congress of Rheumatology. To develop the draft criteria, data collated from 135 sites in 32 countries on more than 2,000 patients were used. These had been collected as part of the ACR/EULAR–run DCVAS study, which has been coordinated at the University of Oxford since 2011.
Three phases were used to develop these criteria: first an expert panel reviewed all cases in the DCVAS to identify those that they felt were attributable to small vessel vasculitis. Second, variables that might be appropriate to use in the models were examined, with more than 8,000 individual DVCAS items considered and then whittled down to 91 items and then sifted again to form a clear set of 10 or fewer items. Third, statistical analyses combined with expert review were used to develop the criteria and then validate these.
Dr. Robson reported that of 2,871 cases identified as ANCA-associated vasculitis, 2,072 (72%) were agreed upon by the expert review panel. Of these, there were 724 cases of GPA, 291 of MPA, 226 of EGPA, and around 300 cases of other small vessel vasculitis or polyarteritis nodosa. To develop the criteria the GPA cases were used as the “cases” and the other types of vasculitis as the comparators, Dr. Robson explained.
For GPA, MPA, and EGPA a set of items (10, 6, and 7, respectively) were derived and scored, positively or negatively, and a cutoff determined at which a classification of the particular vasculitis could be made. During discussion, Dr. Robson noted that the threshold score for a classification of EGPA (greater than or equal to 6) had been set slightly higher than for GPA or MPA (both greater than or equal to 5) “because of the clinical problem of there being very close comparators which can actually mimic EGPA.” This is where the negative scoring of some items used in these criteria are very important, she said.