If your GP suspects you have giant cell arteritis (GCA), they'll ask you about your symptoms and examine your head.
This is because giant cell arteritis can cause physical signs, such as noticeably swollen arteries in your temples.
If your GP suspects you may have giant cell arteritis, they'll refer you for blood tests to help assess the levels of inflammation inside your body.
Two blood tests that you may have are erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP). These tests are useful for assessing conditions associated with short- or long-term inflammation.
Lab Tests Online UK has more information about ESR and CRP tests.
If you have vision problems, it's likely your GP will arrange a same-day appointment with an eye specialist (ophthalmologist). This will usually be at your local hospital or eye clinic.
The ophthalmologist will check your eyes for changes associated with giant cell arteritis, such as bleeding or swelling at the site of your optic nerve (the nerve at the back of the eye that transmits signals to the brain).
Temporal artery biopsy
A temporal artery biopsy is most commonly used to test for giant cell arteritis.
During the procedure, the skin on the side of your head is numbed with a local anaesthetic. An incision is made close to the hairline in front of your ear, and a small sample of your temporal artery is removed. The incision will then be sealed with stitches.
The sample can be studied under a microscope in a laboratory to check for damage and inflammation of the lining of the arteries. It can take several days to get the results of a biopsy.
If giant cell arteritis is suspected, treatment with steroid medication (corticosteroids) will usually begin immediately. Waiting until the results of the biopsy are known could affect your sight.
Read more about treating giant cell arteritis.
Research has shown cranial ultrasound is a simple and accurate diagnostic test for giant cell arteritis. However, the procedure is still quite new and there are only a few rheumatologists in the UK who carry out the technique, so availability is currently limited.
Accurately diagnosing giant cell arteritis is very important because it ensures people with the condition continue to receive steroid treatment to help prevent visual impairment.
This also ensures that those who no longer have the condition don't continue receiving steroid treatment unnecessarily. Long-term steroid use can cause side effects.