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%