The most accurate way to diagnosis gout is to check your joints for the presence of crystals. However, this test is often not practical to carry out at your local GP.
Instead, usually your GP will look at your symptoms and medical history to make a diagnosis.
Many conditions can cause jointpain, inflammation and swelling. Gout is just one of over 200 different forms of arthritis (any condition that causes pain and problems with the joints).
Therefore, your GP may be unable to make a firm diagnosis straight away and you may be referred for further tests. These will either confirm the diagnosis of gout or rule out other conditions.
Serum uric acid
A serum uric acid test is usually carried out four-to-six weeks after an attack of gout, as the serum uric acid level is often not raised at the time of the attack.
The test involves analysing a sample of blood taken from a vein in your arm to measure the amount of uric acid in your blood.
A raised uric acid level is often an indication you may have developed gout. However, a serum uric acid test is not definitive. Some healthy people without gout have high uric acid levels in their blood, while others who experience an attack of gout have a normal level.
If there is any doubt about what is causing your joint pain, you may have a sample of synovial fluid taken from the affected joint. Synovial fluid helps to keep the joint lubricated and stops the bones and cartilage from rubbing against each other.
The fluid sample is taken using a needle and syringe. It is then examined under a microscope. If you have gout, there will nearly always be crystals of sodium urate in the sample. This sort of test will also help to rule out other crystals (calcium pyrophosphate) that can cause similar attacks of inflammation, as well as an infection in the joint such as septic arthritis (when a joint becomes infected with bacteria).
An X-ray is rarely used to diagnose gout because inflammation caused by gout is not usually detectable using this method. However, an X-ray is sometimes used to help rule out other conditions that affect the joints, such as chondrocalcinosis (a build-up of calcium crystals in the joints).
Confirming the diagnosis
As checking the joints for crystals is not always practical in general practice, a checklist is often used. This is based on the known pattern of symptoms associated with the condition.
The checklist used is as follows:
- You have had more than one attack with symptoms of pain, swelling and inflammation.
- You have experienced high levels of inflammation within just one day of the onset of symptoms.
- Symptoms only affect one joint at a time.
- The joint in your big toe or other foot joints have been affected.
- Results of the serum acid test show raised levels of uric acid in your blood.
- Physical examination or X-rays have detected swelling within a joint.
- There is no evidence that your joint has been infected by bacteria.
You will usually be diagnosed with gout if at least six of the statements above apply to you.
About four-to-six weeks after your gout attack has subsided, your GP may ask you to return for a follow-up appointment to check your serum uric acid level.
Your GP can also give you an advance prescription of painkilling medication so that you can deal with attacks of gout promptly.
Read more about treating gout.
- Blood supplies oxygen to the body and removes carbon dioxide. It is pumped around the body by the heart.
- Blood test
- During a blood test, a sample of blood is taken from a vein using a needle so it can be examined in a laboratory.
- Joints are the connection point between two bones that allow movement.