Classification, epidemiology and clinical subgrouping of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis

Abstract

It is now 25 years since the first European studies on vasculitis--the anti-neutrophil cytoplasmic antibody (ANCA) standardization project. Over that period of time, there have been major developments in the classification of the vasculitides, which has permitted the conduct of high-quality epidemiology studies. Studying the epidemiology of rare diseases such as the ANCA-associated vasculitides (AAV) poses considerable challenges to epidemiologists. The first is the need for a clear definition of a case with good differentiation from similar disorders. The second is case capture. The vasculitides are rare, and therefore, a large population is required to determine the incidence and prevalence, and this poses questions of feasibility. A large population increases the risk of incomplete case detection but permits a reasonable number of cases to be collected in a practicable time frame, whereas a smaller population requires a much longer time frame to collect the necessary cases, which may also not be feasible. Statistical methods of capture-recapture analysis enable estimates to be made of the number of missing cases. The third is case ascertainment. The AAV are virtually always managed in secondary care, and therefore, hospital-based case ascertainment may be appropriate. Fourthly, the rarity of the conditions makes prospective case-control studies investigating risk factors difficult to conduct because the population size required to achieve statistical confidence is in excess of that which is readily available. Thus, much of the data on risk factors are derived from retrospective studies with inherent potential bias.

ANCA-associated vasculitis

“…3 GPA, MPA and EGPA have respective annual incidence rates of 2.1-14.4, 2.4-10.1 and 0.5-3.7 per million in Europe, and the prevalence of AAV is estimated at to be 46-184 per million. 4 They are more common in those aged over 60 years and slightly more common in men. The 5-year survival rates for GPA, MPA and EGPA are estimated to be 74-91%, 45-76% and 60-97%, respectively.…”

The Prevalence and Management of Pauci-Immune Glomerulonephritis and Vasculitis in Western Countries

“…In the European population, the incidence is reported to be 1-2 cases in 100,000 [7,9], with an increasing trend in recent years up to 2000 [10], which may be a consequence of an actual increase in disease frequency, increased awareness among physicians, and better ability of disease recognition through the introduction of ANCA testing. However, since the incidence has been stable since the early 2000s, it is most likely that increased physician awareness following the introduction of ANCA testing in routine clinical practice is the most likely reason [11]. Moreover, the incidence of GPA is higher than that of MPA in Northern Europe, while MPA is predominant among cases of AAV in Southern Europe [11,12,13].…”

“…However, since the incidence has been stable since the early 2000s, it is most likely that increased physician awareness following the introduction of ANCA testing in routine clinical practice is the most likely reason [11]. Moreover, the incidence of GPA is higher than that of MPA in Northern Europe, while MPA is predominant among cases of AAV in Southern Europe [11,12,13]. …”

Neurological manifestations in ANCA-associated vasculitis - assessment and treatment

“…Their main common features are necrotizing inflammation of medium to small vessels and association with antineutrophil cytoplasmic antibodies (ANCA) production. AAV is rare with incidence ranging from 15 to 25/1 million in the general population [2]. It has a systemic course which means, the disease can affect virtually any organ.…”