Gout is caused by a build up of sodium urate crystals in and around joints due to an increased uric acid level in the blood.
The condition can cause a number of symptoms but the most common are inflammation and pain caused by the crystals irritating the soft lining of the joint called the synovium.
However, pain and inflammation in the joints can be caused by many conditions and gout is only one of 200 forms of arthritis.
Therefore, a patient may be referred for a number of tests before other conditions can be ruled out and gout can be diagnosed.
The most reliable way to confirm a diagnosis of gout is to check for the presence of crystals in the joints. However, this often cannot be carried out at a GP practice and a diagnosis is instead based on a range of tests, medical history and patient symptoms.
An outline of how gout is diagnosed is given below:
- A detailed description of the patient’s symptoms is obtained including their severity, onset and duration. The joint pain that occurs in gout often affects the big toe first, although any joint in the body can be affected. Other symptoms include redness, warmth and swelling in the joint area. The symptoms usually develop rapidly and pain becomes the most intense within just 6 to 24 hours of onset. This is referred to as a “gout attack”. The symptoms can last for between three and ten days, after which the joint starts to feel normal again and the pain subsides.
- Any family history of the condition is also obtained to assess the likelihood that the patient may be genetically predisposed to developing gout.
- A patient is asked about their diet to establish whether or not the foods they eat are typically rich in purines, substances which are broken down into uric acid in the body.
- The uric acid level in the blood is tested around four to six weeks after a gout attack as the uric acid level is often not raised immediately after an attack. However, diagnosis cannot be based on this test alone because some people without gout have a high uric acid level, while others who do have gout present with a normal uric acid level.
- A sample of the synovial fluid may be taken from the joint to rule out infection and the presence of other crystals that can cause symptoms similar to gout. The presence of sodium urate crystals in the joint almost always means gout can be diagnosed.
- Occasionally, an X-ray may be taken to help rule out other conditions that affect joints.
- An ultrasound scan can be performed to check for sodium urate crystals in the joint.
Reviewed by Sally Robertson, BSc