Prevalence of Wegener's granulomatosis, microscopic polyangiitis, polyarteritis nodosa and Churg-Strauss syndrome within a defined population in southern Sweden

OBJECTIVES: To estimate the point prevalence (p.p.) of Wegener's granulomatosis (WG), microscopic polyangiitis (MPA), polyarteritis nodosa (PAN) and Churg-Strauss syndrome (CSS) within a defined population in southern Sweden. METHOD: A cross-sectional p.p. study using multiple sources for case identification. The study area, a healthcare district around the city of Lund in southern Sweden (Mellersta Sk?nes sjukv?rdsdistrikt), had, on 31 December 2002, a total population of 287 479 inhabitants. All the identified cases were verified by medical record review. The patients were classified according to an algorithm based on the American College of Rheumatology classification criteria 1990 and the Chapel Hill Consensus Conference definitions 1994. RESULTS: Eighty-six patients (49% female) with a median age of 64.8 yrs (range 15-90.5) fulfilled the study criteria. There were 46 patients with WG; 27 with MPA; nine with PAN; and four with CSS. The p.p. per million inhabitants was estimated on 1 January 2003 to be 160 (95% confidence interval 114-206) for WG, 94 (58-129) for MPA, 31 (11-52) for PAN and 14 (0.3-27) for CSS. Capture-recapture analysis estimated the completeness of the case finding to 96%. CONCLUSIONS: The prevalence of WG, MPA, PAN and CSS in our district is the highest figure reported so far. Explanations for this finding may include high incidence, extensive ANCA-testing, good survival as well as sensitive search methods for case identification.