Gout - Diagnosis

Blood Test for Uric Acid Levels

A blood test is usually given for measuring uric acid and detecting hyperuricemia. A low level of uric acid in the blood makes a diagnosis of gout much less probable, and a very high level increases the likelihood of gout. Some experts argue, however, that such measurements are not very useful, given what is known about the variability of uric acid levels in people with gout:

Uric acid levels in the blood during an attack of gout can lie within or below the normal range.
Even if hyperuricemia is present, it is very common in the population and does not necessarily indicate the presence of gout.

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Determining Uric Acid Excretion in Urine

It is sometimes helpful to gauge the amount of uric acid excreted by the patient, particularly if the patient is young and has pronounced hyperuricemia that might be related to a metabolic disorder. If uric acid exceeds a particular value in the urine, further tests for an enzyme defect or other identifiable cause of gout arising from uric acid overproduction are justified. Greater-than-normal amounts of uric acid in the urine also indicate that the patient faces a greater risk of developing uric acid kidney stones, and can guide the physician in his or her choice of drug therapy for chronic gout.

24-Hour Urine Sample. Typically, urine samples are taken over the course of 24 hours. To provide a urine sample, the following steps are taken:

The urine is collected during an intercritical period, after the patient has been placed on a purine-reduced diet. The patient is also asked to temporarily stop using alcohol and any medications that can interfere with the test.
The patient should not change any of his or her usual eating or drinking patterns when performing this test.
The patient discards the first urination on the day of the test.
Afterward all urine passed over the next 24 hours is collected, including the first urination on the morning of day two.
The container is then delivered to the patient?s physician or sent directly to the laboratory.

Click the icon to see an image of a uric acid test.

Imaging Techniques

X-Rays. For the most part, x-rays do not reveal any abnormalities during the early stages of gout, and their usefulness where gout is concerned lies in assessing the progress of the disorder in its chronic phase and in identifying other health problems whose symptoms may resemble those of gout. Tophi can be seen on x-rays before they become apparent on physical examination.

Advanced Imaging Techniques. Advanced imaging techniques being investigated for identifying tophi include computed tomography (CT), magnetic resonance imaging (MRI), and Doppler ultrasonography. A 2002 study comparing these approaches found that CT scans offered the best images.