Primary renal vasculitis in Norfolk--increasing incidence or increasing recognition?

Area of Science:

• Nephrology
• Rheumatology
• Epidemiology

Background:

• Previous estimates of renal vasculitis incidence relied on limited diagnostic criteria.
• The Norwich Health Authority (NHA) provides a unique, stable population for incidence studies.
• This study aimed to determine the incidence of primary renal vasculitis and its subtypes within the NHA.

Purpose of the Study:

• To accurately estimate the overall incidence of primary renal vasculitis.
• To determine the incidence of individual clinical classifications of renal vasculitis.
• To compare Norfolk's incidence rates with previous European and global estimates.

Main Methods:

• Retrospective review of renal biopsies, vasculitis registers, and hospital records from 1992-1997.
• Classification of patients using established criteria (ACR, Chapel Hill, Lanham).
• Incidence calculation based on the NHA adult population (413,747 in 1994).

Main Results:

• Overall annual incidence of primary renal vasculitis was 18/million.
• Specific annual incidences: Wegener's Granulomatosis (WG) 7.9/million, Microscopic Polyangiitis (mPA) 7.5/million, Polyarteritis Nodosa (PAN) 7.0/million, Henoch-Schonlein Purpura (HSP) 3.1/million, Churg Strauss Syndrome (CSS) 1.3/million.
• Incidence rates were higher than previously reported European estimates.

Conclusions:

• The incidence of primary renal vasculitis in Norfolk is significantly higher than previously reported in Europe.
• Observed variations in incidence may indicate true population differences or underestimation in prior studies.
• Findings have implications for understanding the aetiology of primary vasculitis and potential geographical variations.