Berti A, et al. – This population-based study was meant to estimate the incidence, prevalence, and mortality of ANCA-associated vasculitis (AAV) and its subsets, granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA) and eosinophilic GPA (EGPA), in Minnesota (USA). Collected data showed that the annual incidence of AAV in Olmsted County was 3.3/100,000, with the prevalence of 42.1/100,000, significantly higher than reported in other areas worldwide. However, the incidence of GPA and MPA was similar. Mortality of MPA and EGPA, but not GPA, was higher than the general population. MPO-ANCA served as a marker of poor survival.

Methods

• The clinicians reviewed all the medical records of patients with a diagnosis or suspicion of AAV in Olmsted County, Minnesota from January 1, 1996 to December 31, 2015.
• Incidence rates were age- and sex-adjusted to the 2010 US white population.
•  Age- and sex-adjusted prevalence was calculated on January 1, 2015.
•  In the Minnesota population, survival rates were compared with expected rates.

Results

• Out of 58 incident cases of AAV, 23 (40%) were GPA, 28 (48%) MPA, and 7 (12%) EGPA.
• 28 (48%) were women, 57 (98%) were Caucasian, with a mean±SD age at diagnosis of 61.1±16.5 years.
• 34 patients (61%) were MPO-ANCA and 17 (30%) were PR3-ANCA positive; 5 (9%) were ANCA-negative.
• Accumulated data revealed that the annual incidence of AAV was 3.3/100,000 population (95%CI:2.4-4.1).
• GPA, MPA and EGPA incidence was 1.3 (95%CI:0.8-1.8), 1.6 (95%CI:1.0-2.2), and 0.4 (95%CI:0.1-0.6), respectively. 
• Overall prevalence of AAV was 42.1/100,000 (95%CI:29.6-54.6). 
• Mortality for AAV overall, and EGPA, MPA and MPO-ANCA was increased (p<0.05).
• Mortality of GPA, PR3-ANCA and ANCA-negative patients did not differ from general population.