Making the Diagnosis
GCA is diagnosed by a thorough physical examination, blood tests, and sometimes by taking a biopsy (tissue sample) of the affected temporal arteries. Two tests, the erythrocyte sedimentation rate (ESR) and C-reactive protein, are usually elevated in GCA. The ESR measures how fast erythrocytes (red blood cells) settle to the bottom of a thin test tube.
It may be necessary to do tests that take images of the blood vessels in the chest and neck and to check for signs of heart damage. GCA can damage the aorta (the largest artery in the body, which originates in the heart) and other major vessels. Tests such as ultrasound, MRA, and PET scans of the temporal artery can take images in a non-invasive manner. Sometimes, an angiogram needs to be done.
If a biopsy is needed, usually at least an inch (2.54 centimeters) is removed from the temporal artery, sometimes from both sides of the forehead. Taking two samples can give a more reliable diagnosis.
Note that arteritis is an acute inflammation of the arteries, which is different from atherosclerosis, which is hardening of the arteries that occurs gradually.