A diagnosis of giant cell arteritis (GCA) is based on:
- your symptoms
- a clinical examination
- blood tests
- a temporal artery biopsy
- an ultrasound scan.
It’s very important that your GP starts treatment straight away if GCA is suspected. However, you should also be referred promptly to a specialist to confirm the diagnosis. This may either be an ophthalmologist (an eye specialist) or a rheumatologist (a doctor who specialises in immune problems and problems with the joints and muscles).
What tests will I have for GCA?
These are used to check for signs of inflammation in the blood vessels. They’re useful in diagnosing GCA, but will also be repeated over time to check that the inflammation is controlled.
The key blood tests are the C-reactive protein (CRP) and the erythrocyte sedimentation rate (ESR). The levels measured by both these tests increase when there’s inflammation in the body. Your doctor may do one or the other of these blood tests. In most cases, ESP and CRP are high in people who have GCA. However, a normal result doesn't necessarily rule out GCA, and inflammation may have other causes such as infection.
Other blood tests may be done to look for other possible causes for your symptoms, including tests to check for inflammation in other blood vessels.
You may be asked to have a chest x-ray to rule out other conditions.
Your doctor may ask for an ultrasound scan of the arteries overlying the temple and in the armpit. This can be helpful in confirming a suspected GCA diagnosis, in combination with a biopsy. However, this type of scan isn't yet available in all hospitals.
Temporal artery biopsy
You may be given a biopsy even if you’ve already started on steroid treatment. The test should be done within 1–2 weeks of starting steroids. After this time, the steroids may be starting to work, making the test less reliable.
There are three main reasons for having the test:
- It can confirm the diagnosis or sometimes suggest a different diagnosis. This is important to avoid unnecessary steroid treatment.
- If your condition doesn’t improve with steroid treatments, it may be that you don’t have GCA. If the test shows no signs of GCA and your doctor is satisfied that you don’t have GCA the steroid treatment can be stopped.
- It may help in assessing how severe the condition is and whether more powerful treatments are needed.
Using local anaesthetic, a small sample of artery from the scalp over your temple is removed and examined under a microscope. Your doctor will explain the procedure, including the risks and benefits, and you’ll be asked to sign a form consenting to the biopsy.
After the biopsy is taken you’ll have a wound about 3–4 cm (1–1½ in.) in length, close to the hairline. The wound will be covered with a dressing until your follow-up appointment about a week later, but you will be able to wash your hair with care. When the anaesthetic wears off you may need painkillers such as paracetamol for a time.
As with any surgical procedure you should look out for signs of infection – such as redness which starts to spread or a continuous discharge. Very rarely, the procedure may lead to temporary or permanent damage to the nerves which may result in numbness or a drooping brow. In patients who have narrowing of the arteries in the neck (carotid artery disease) there may be a very small risk of a stroke. If you have any concerns about the risks you should discuss them with your doctor beforehand.
Usually, the biopsy will contain enough sample to confirm the diagnosis. But sometimes it may not show evidence of GCA. If this happens, your doctor will decide whether to continue treatment based on blood tests and your overall condition.