Gout is a type of arthritis that is caused by a buildup of uric acid in the blood. Gout patients complain of a sudden onset of redness, swelling and warmth in one joint-- usually the toe, ankle or knee. Attacks usually subside after three to 10 days, and are followed by symptom-free periods before another attack occurs. According to the National Institute for Arthritis and Musculoskeletal and Skin Diseases, it can be difficult to diagnose gout because the symptoms are not necessarily specific to the disease. If your doctor suspects that you may have gout, several tests are available to assist in diagnosing the disease or ruling it out.
Blood Test for Uric Acid
There is no blood test that is specific to gout, but determining if the uric acid level is higher than normal can be somewhat helpful. Uric acid, a byproduct of purine breakdown, is normally excreted in the urine, but it can build up in the bloodstream if the kidneys are not working properly or if too much is produced in the body. Purines are chemicals that occur naturally in the body and in some foods, including anchovies, liver, mackerel, dried beans and peas, wine and beer. High uric acid levels are associated with a number of diseases, including gout, diabetes, kidney failure, toxemia of pregnancy and other conditions. Patients with gout may have high levels of uric acid in their blood (hyperuricemia), but many people with hyperuricemia do not develop gout.
Blood Tests to Rule Out Other Diseases
Your doctor may order tests specific for other types of arthritis to rule them out. These tests may include tests for rheumatoid factor (RF) or antinuclear antibody (ANA). If infection of the joint or septic arthritis is a possibility, a blood culture will be ordered. Chemistry panels (tests for calcium, potassium, sodium, glucose, chloride, carbon dioxide, blood urea nitrogen and creatinine) screen for kidney damage and other underlying conditions.
Synovial Fluid
If gout is suspected, your health care provider may withdraw a sample of fluid from your inflamed joint to check for uric acid crystals. If the crystals are detected, the diagnosis of gout is confirmed, but according to the American Society for Clinical Chemistry, the absence of uric acid crystals does not eliminate the possibility of gout. The sample can also be examined for red and white blood cells and bacteria to rule out injury and infection.
Physical Examination
The doctor may be able to see or feel uric acid crystals around the joint, confirming the diagnosis of gout.
X-rays
Your doctor may order X-rays of the affected joint to look for uric acid deposits and damage from previous gout attacks.
