Diagnosis is based on clinical features and investigations:
- clinical presentation
- blood tests:
- ESR usually raised
- platelet count usually raised
- eosinophilia is not usually a feature, in contrast to polyarteritis nodosa and Churg-Strauss syndrome
- chest radiology:
- flitting pulmonary infiltrates
- bilateral nodules or masses which may cavitate
- mediastinal or hilar lymphadenopathy is rare
- urinalysis is a sensitive means of detecting renal involvement, and an active urinary sediment with red blood cells (RBC) and casts indicates glomerular disease
- serum urea and creatinine may be normal despite active renal disease
- renal biopsy will serve to confirm the diagnosis and document the extent of renal inflammation or scarring
- urinalysis is the single most important investigation. The extent of renal impairment and rate of deterioration in renal function is a major determinant of prognosis. The detection of proteinuria and/or haematuria in a patient with a systemic illness mandates immediate further investigation and is a medical emergency (1)
- histological demonstration of granulomata in the respiratory tract
- histological examination of the kidney will reveal characteristic focal necrotizing glomerulonephritis:
- in advanced cases there may be widespread crescent formation around the glomeruli
- evidence of vasculitic changes in small arterioles, veins and capillaries
- over 90% of patients with Granulomatosis with polyangiitis (GPA) are C-ANCA positive
- initial screening of all sera by indirect immunofluorescence on ethanol-fixed neutrophils to discriminate 2 main patterns of ANCA: a cytoplasmic pattern (c-ANCA) and a perinuclear pattern (p-ANCA)
- pattern obtained should then be confirmed by a more specific ELISA test, specifically for antiproteinase 3 and antimyeloperoxidase
- combined approach of immunofluorescence and ELISA produces sensitivity of 73% and a diagnostic specificity of 99% (2)
The diagnostic criteria, as defined by the American College of Rheumatology for the diagnosis of Wegener's granulomatosis requires at least 2 of the following 4 criteria (3):
(1) oral ulcers or nasal discharge,
(2) the presence of nodules, fixed infiltrate, or cavities on a chest radiograph,
(3) nephritic urinary sediment (red cell cast or >5 red blood cell per high power field),
and (4) granulomatous inflammation on a biopsy
Note though that oral ulceration generally occurs late in the disease (2).
Reference:
- ARC Autumn 2012. Topical Reviews - ANCA-associated vasculitis; 1:1-12.
- Ponniah I et al. Wegener's granulomatosis: The current understanding. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2005 Sep;100(3):265-70.
- Rao JK et al. Limitations of the 1990 American College of Rheumatology Classification Criteria in the diagnosis of vasculitis, Ann Intern Med 1998;129: 345-352.