Diagnosis

Giant cell arteritis can be difficult to diagnose because its early symptoms resemble those of other common conditions. For this reason, your doctor will try to rule out other possible causes of your problem.

In addition to asking about your symptoms and medical history, your doctor is likely to perform a thorough physical exam, paying particular attention to your temporal arteries. Often, one or both of these arteries are tender, with a reduced pulse and a hard, cordlike feel and appearance.

Your doctor might also recommend certain tests.

Blood tests

The following tests might be used to help diagnose your condition and to follow your progress during treatment.

• Erythrocyte sedimentation rate. Commonly referred to as the sed rate, this test measures how quickly red blood cells fall to the bottom of a tube of blood. Red cells that drop rapidly might indicate inflammation in your body.
• C-reactive protein (CRP). This measures a substance your liver produces when inflammation is present.

Imaging tests

These might be used to diagnose giant cell arteritis and to monitor your response to treatment. Tests might include:

• Doppler ultrasound. This test uses sound waves to produce images of blood flowing through your blood vessels.
• Magnetic resonance angiography (MRA). This test combines an MRI with the use of a contrast material that produces detailed images of your blood vessels. Let your doctor know ahead of time if you're uncomfortable being confined in a small space because the test is conducted in a tube-shaped machine.
• Positron emission tomography (PET). If your doctor suspects you might have giant cell arteritis in large arteries, such as your aorta, he or she might recommend PET. This test uses an intravenous tracer solution that contains a tiny amount of radioactive material. A PET scan can produce detailed images of your larger blood vessels and highlight areas of inflammation.

Biopsy

The best way to confirm a diagnosis of giant cell arteritis is by taking a small sample (biopsy) of the temporal artery. This artery is situated close to the skin just in front of your ears and continues up to your scalp. The procedure is performed on an outpatient basis using local anesthesia, usually with little discomfort or scarring. The sample is examined under a microscope in a laboratory.

If you have giant cell arteritis, the artery will often show inflammation that includes abnormally large cells, called giant cells, which give the disease its name. It's possible to have giant cell arteritis and have a negative biopsy result.

If the results aren't clear, your doctor might advise another temporal artery biopsy on the other side of your head.