Observational StudyAmerican College of Rheumatology/European League Against Rheumatism (ACR/EULAR) Diagnostic and Classification Criteria for Primary Systemic Vasculitis

Vasculitis is group of diseases where inflammation of blood vessels is the common feature. Patients typically present with fever, fatigue, weakness and muscle and joint aches. These symptoms are very common among many different diseases, not just vasculitis. A clustering of other symptoms, physical examination findings, blood tests, radiology and biopsy help make the diagnosis. There are currently no criteria to help doctors make a diagnosis of vasculitis when a patient presents with these non specific symptoms and they are reliant on previous experience and disease definitions. One of the aims of this project is to develop diagnostic criteria for the primary systemic vasculitides (granulomatosis with polyangiitis (Wegener's), microscopic polyangiitis, Churg Strauss syndrome, polyarteritis nodosa, giant cell arteritis, Takayasu arteritis). We, the investigators, will do this by studying a large group of patients with vasculitis and comparing them to a large group of patients that present in a similar way, but do not have vasculitis. By comparing the 2 groups we will create a list of items to differentiate between vasculitis and 'vasculitis mimics'.

We also aim to update the current classification criteria. Classification criteria are used to group patients into different types of vasculitis, once a diagnosis of vasculitis has been made, and are useful for studying patients in clinical trials with similar or identical diseases. The current classification criteria (American college of Rheumatology 1990 criteria) were developed 20 years ago, before the availability of some important diagnostic tests (e.g. antineutrophil cytoplasmic antibodies \[ANCA\]), and are now not consistent with some of the current disease definitions. Therefore to progress future research in vasculitis, it is important that the classification criteria are updated. We will recruit 260 patients with each of the 6 types of vasculitis and compare them with 1300 controls (patients with the 5 other types of vasculitis), in order to determine the optimal combination of symptoms, signs and investigations that classify each person into the appropriate group.