Gout Diagnosis

• When to see a doctor
• Tests used to diagnose gout
• Conditions with similar symptoms

When to see a doctor

For most people, the first sign of gout is an attack of arthritis. Gout attacks are characterized by sudden pain, swelling, or redness in a joint. If you experience these symptoms, it's important to visit a doctor to get a diagnosis and treatment plan.

There are many other possible causes of joint pain and swelling. Many of these conditions can be mistaken for gout but they are treated differently. A doctor will perform a physical examination, ask questions about your symptoms, family history of gout, age, sex, and other risk factors to make a diagnosis.

Your primary care doctor may refer you to a specialist called a rheumatologist. Rheumatologists specialize in gout and other forms of arthritis.

Tests used to diagnose gout

If your doctor suspects you have gout, they will most likely run tests to help diagnose gout. These tests for gout may include:

• Blood tests. Your doctor will want to run a blood test to check your uric acid levels. When levels are consistently above 6.8 milligrams per deciliter (mg/dL), the uric acid can form crystals in the joint, leading to joint inflammation typical of a gout attack.

However, not everyone with uric acid above this level develops gout. Just having high uric acid levels is not enough to make a diagnosis of gout. Still, the blood test is useful both for contributing to the diagnosis and for monitoring uric acid levels in people on long-term medication to treat gout.

• Joint fluid test. The test that can definitively diagnose gout is arthrocentesis, which is also called joint aspiration or a joint tap. Your doctor will numb the area around an inflamed joint and remove some fluid using a fine, hollow needle. The fluid is then examined under a special type of microscope to look for the telltale uric acid crystals.

This test is commonly performed when the doctor is uncertain whether gout, an infection, or another condition is causing the symptoms.

• Ultrasound. This technique uses sound waves to detect fluid and inflammation in soft tissues and abnormalities in muscles or tendons.Ultrasound also can show evidence of crystals and tophi (which are visible, lumpy deposits of uric acid crystals under the skin that can appear around joints) that are signs of gout.
• Dual-energy computerized tomography (DECT). This type of x-ray can produce three-dimensional images that show structures other than bone. DECT may be used to see uric acid crystals in the joints.

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Conditions with similar symptoms

Several conditions involving the joints can be mistaken for gout, which is why it is important to see a doctor for a proper diagnosis. Conditions with symptoms similar to gout include the following:

• Pseudogout. Gout and pseudogout - more formally called calcium pyrophosphate dihydrate crystal deposition (CPPD) disease - are both painful arthritic conditions but are caused by different crystals. With gout, needle-shaped crystals of uric acid cause inflammation. However, with pseudogout, the crystals are caused by a substance called calcium pyrophosphate dihydrate. 

It's relatively common for deposits of CPPD to build up in joints over time. About half of people over age 80 have them.  But only some people with CPPD deposits develop symptoms, usually in the knee.

To know for sure whether joint symptoms are caused by pseudogout or gout, a doctor may draw some fluid from the joint and examine it under a microscope.  

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• Septic arthritis. This is a joint infection that is usually caused by bacteria. Septic arthritis can develop if an infection spreads from elsewhere in the body. Infections also can begin at the joint itself after a puncture wound, injection, or surgery. Symptoms include pain, redness, swelling, and fever. Blood tests, imaging tests, or arthrocentesis can be used to confirm a joint infection.
• Reactive arthritis.Reactive arthritis occurs in reaction to an infection by certain bacteria. Infections that can lead to reactive arthritis include Chlamydia trachomatis, which is sexually transmitted, and infections in the gastrointestinal tract .

Reactive arthritis may be mistaken for gout as it causes joint pain, swelling, and                  stiffness, usually two to four weeks after the infection. The joints most commonly       affected are the knees, ankles, and toes, which are the same joints often affected by        gout.

• IBD-associated arthritis. Inflammatory bowel disease (IBD) is a group of diseases that involve long-term inflammation of the gastrointestinal tract. People with IBD can develop a form of arthritis that may affect joints in the spine or other joints, such as the knees, hips, shoulders, fingers, and feet. Joint symptoms may occur at the same time as flare-ups of intestinal symptoms.

Related: Chronic gut inflammation: Coping with inflammatory bowel disease

• Psoriatic arthritis. This form of arthritis sometimes occurs in people who have psoriasis, a disease that causes red, scaly patches of skin. Symptoms include joint pain, redness, and swelling, as well as pain in the feet and lower back.
• Osteoarthritis. The most common form of arthritis, osteoarthritis, is caused by the wearing down of cartilage that cushions the ends of bones. As a result, bone rubs against bone at the joints, causing pain, stiffness, and swelling. The symptoms tend to be mild at first and grow more intense over time. However, they can come and go as well. The pain typically occurs only while the joint is in motion. This differs from a gout attack, which causes symptoms even when the joint is at rest.