A tissue biopsy is the gold standard test for diagnosis of vasculitis. It involves taking a tissue sample from a blood vessel or affected organ and examining it for signs of inflammation or damage. (For more details, see the article on Anatomic Pathology: Histopathology.)
Before taking a biopsy, which is invasive, certain laboratory and non-laboratory tests can be performed to determine which organs are involved. Several of these tests are also used to monitor treatment.
- Complete blood count (CBC) – this test is used to look for complications of vasculitis and its treatment. It evaluates a person's red blood cells and hemoglobin for anemia and checks the white blood cell count, which can be increased in infection or reduced following some treatments. Increased numbers of white blood cells are seen with some types of vasculitis, such as eosinophilic granulomatosis with polyangiitis, EGPA (Churg-Strauss Syndrome).
- C-reactive protein (CRP) - this test detects inflammation in the body.
- Erythrocyte sedimentation rate (ESR) – this test also detects the presence of inflammation and can be increased in several types of vasculitis, such as microscopic polyangiitis and granulomatosis with polyangiitis (Wegener granulomatosis).
- Creatinine – this test assesses kidney function, which may be affected by vasculitis.
- Liver panel – these tests assess liver function to determine if the vasculitis is affecting the liver.
- Urinalysis – this test looks for the presence of protein and red blood cells in the urine, which can indicate inflammation within the kidney.
- Anti-neutrophil cytoplasmic antibody (ANCA) – this test is a useful marker for some systemic vasculitis conditions, such as granulomatosis with polyangiitis and microscopic polyangiitis.
- Complement – part of the inflammatory response; often reduced with vasculitis
- Lung function tests – to determine if airflow is restricted when vasculitis is affecting the lungs
- Cardiac tests – EKG, echocardiography
- Imaging studies – chest x-ray, CT scan, MRI, abdominal ultrasound, angiography
- Nerve conduction studies or nerve biopsy may be useful if there are symptoms of numbness or tingling.
For more on imaging studies, see the web site RadiologyInfo.org.