What Tests Are Used to Diagnose Wegener's?
Most blood tests can only suggest that a person has inflammation somewhere in the body. Anemia (low red blood cell count), an elevated white blood cell count and platelet count, and an elevated sedimentation rate are commonly found in people with Wegener's granulomatosis.
If the kidneys are involved, a healthcare provider can see red blood cells and structures called red blood cell casts in the urine when viewed under a microscope, and the blood tests measuring kidney function may show abnormalities.
Many people with active Wegener's granulomatosis have a blood test that shows the presence of a specific type of antibody (a disease-fighting protein) called antineutrophil cytoplasmic antibodies, or ANCA. Although a positive ANCA test is useful to support a suspected diagnosis of Wegener's granulomatosis, in most instances, healthcare providers do not use it by itself to diagnose this disorder. The ANCA test may be negative in some people with active Wegener's granulomatosis.
X-ray results can be helpful in diagnosing Wegener's granulomatosis. People with lung problems will have abnormal chest x-rays. CT (computed tomography) scans in people with sinus problems may show thickening of the sinus lining.
Currently, the only clear-cut way to diagnose Wegener's granulomatosis is by performing a biopsy (removing a tiny piece of tissue) of an involved organ (usually the sinuses, lung, or kidney).
A healthcare provider will examine tissue from the organ under a microscope to confirm the presence of vasculitis and granulomas (a specific type of inflammation), which together are features of Wegener's granulomatosis.
A biopsy is important -- both to confirm the presence of Wegener's granulomatosis and also to make sure other disorders that may have similar signs and symptoms are not present.