According to the 1990 American College of Rheumatology criteria, two of the following are required for a diagnosis of granulomatosis with polyangiitis to be made:
- positive biopsy for granulomatous vasculitis
- urinary sediment with red blood cells
- abnormal chest radiograph
- oral or nasal inflammation
The classic triad of organ involvement consists of:
- lungs: involved in ~95% of cases
- upper respiratory tract / sinuses: ~75-90%
- kidneys: ~80%