ACR/EULAR Endorsed Study to Develop New Diagnostic and Classification Criteria for Primary Systemic Vasculitis

The systemic vasculitides are a group of uncommon but important diseases whose prognosis has improved dramatically with the use of immunosuppressive therapy. However, long-term morbidity from recurrent disease flares, low-grade grumbling disease and/or accumulating damage from previous disease activity or drug therapy now characterise the long-term outlook for patients with vasculitis. There remains major controversy, and incompatibility between the ANCA-associated vasculitides: granulomatosis with polyangiitis (Wegener's), microscopic polyangiitis, and Churg Strauss Syndrome, as well as polyarteritis nodosa in the current classification criteria and disease definitions. Importantly, there are no diagnostic criteria for any of the primary systemic vasculitides.

We propose to improve existing classification criteria for the primary systemic vasculitides. As a starting point will include the following diseases: granulomatosis with polyangiitis (Wegener's) (GPA), microscopic polyangiitis (MPA), Churg Strauss syndrome (CSS), polyarteritis nodosa (PAN), giant cell arteritis (GCA) and Takayasu arteritis (TAK).

We propose to develop and validate classification and diagnostic criteria for primary systemic vasculitis using the guidelines suggested by the Classification and Response Criteria Subcommittee of the American College of Rheumatology Committee on Quality Measures. For all patients, a detailed medical history, physical examination, laboratory tests (including ANCA), radiology (including angiography), biopsy results, treatment, Birmingham Vasculitis Activity Score (BVAS)version 3, Vasculitis Damage Index (VDI), will be collected. The exact list of items to be recorded will be determined by the expert panel at the start of the study.

Classification criteria

We will study a minimum of 100 patients (new and existing patients) prospectively within each currently defined disease category (GPA, CSS, MPA, PAN, GCA, TAK) for the development of the classification criteria. We anticipate the need to recruit 130 patients to account for misdiagnosis and dropout to achieve the target of 100 with the confirmed reference diagnosis. This will include patients that have vasculitis which are assumed to be related to ANCA but do not fulfil the current definitions of any of the diseases, and patients with large vessel vasculitis which do not fulfil current definition for GCA or TAK. Therefore new categories of disease may be created as part of this process and some of the current disease categories may be changed to include or exclude certain patients.