The Role of Gout Tests
Gout testing can be used to diagnose the cause of a person’s symptoms, help doctors plan treatment, and monitor the treatment of gout:
- Diagnosis: Testing for gout helps doctors to identify gout, distinguish it from other conditions, and investigate the cause of increased uric acid concentrations in the blood.
- Determining treatment: For many patients, urate-lowering therapy is the first approach to treating gout. Human leukocyte antigen (HLA) testing is recommended for patients of certain ethnic backgrounds to determine their risk of severe side effects while taking urate-lowering medications.
- Treatment monitoring: Patients being treated for gout may have their uric acid concentration in their blood continuously monitored. Tracking the level of uric acid in the blood can help doctors ensure that the medication is working appropriately.
Who should get testing?
Gout testing may be recommended for patients experiencing symptoms of gout or with a history of suspected gout flares. Indications for gout testing include:
- Joint pain, swelling, and skin redness in one or multiple joints
- Severe pain in the joint at the base of the big toe
- Recurrent inflammation in the inner arch of the foot
- Previous symptomatic attacks that began quickly and resolved on their own
Accurately diagnosing gout is important to ensure appropriate treatment. Symptoms caused by gout are similar to symptoms of other inflammatory conditions, making it important to work with a medical team that specializes in diagnosing and treating gout. Patients concerned about gout may find it helpful to discuss gout testing with a doctor called a rheumatologist, who specializes in diseases of the joints, muscles, and bones.
Testing is also performed in patients who have been diagnosed with and are receiving treatment for gout in order to manage the disease as effectively as possible.
Getting test results
How patients receive gout testing results, and how long it takes to receive them, varies based on the type of test. Tests that require analysis in a specialized laboratory may provide results within a few business days, although some tests take more time. Results may be provided by a doctor’s office or through online medical charts.
Although a single test may be sufficient to diagnose gout, determining the appropriate treatment may depend on results of more than one test.
Types of Gout Tests
The preferred method of diagnosing gout is through a synovial fluid analysis. Synovial fluid is a liquid found in small quantities in the spaces between the joints, where it cushions bone ends and reduces friction during joint movement in the knees, shoulders, hips, hands, and feet.
A synovial fluid analysis consists of a group of tests that detects abnormalities in synovial fluid and diagnoses disorders of the joints. One portion of this analysis involves a microscopic examination of the synovial fluid, called a Gram stain, to look for the needle-like urate crystals that are characteristic of gout, as well as for bacteria and other substances.
Uric acid testing, which uses blood or urine samples to detect elevated levels of uric acid, can support a diagnosis of gout, but results may be misleading. Some patients have normal levels of uric acid in their blood during a gout flare, and many people with increased levels of uric acid don’t develop gout.
While uric acid testing alone cannot diagnose or rule out gout, it is an important part of living with gout. Uric acid testing is conducted several times after a patient is diagnosed with gout in order to determine their baseline level of uric acid. Uric acid is then measured at regular intervals to monitor the effectiveness of gout treatment.
If urate crystals are detected by a synovial fluid analysis, additional tests may not be necessary to diagnose gout. If a synovial fluid analysis is not possible, or the results are inconclusive, doctors can diagnose gout based on a patient’s symptoms, a physical exam, and blood test results. Tests related to diagnosing gout and ruling out other potential causes of joint pain include the following:
|Tests Related to Diagnosing Gout and Related Conditions|
|Test Name||What It Measures|
|Complete Blood Count (CBC)||Blood sample||Many aspects and features of the blood|
|Antibody tests||Blood sample||Antibodies related to specific pathogens|
|Erythrocyte Sedimentation Rate (ESR)||Blood sample||A protein related to inflammation in the body|
|C-Reactive Protein (CRP)||Blood sample||A protein related to inflammation in the body|
|Antinuclear Antibody (ANA)||Blood sample||Autoantibodies present in certain autoimmune disorders|
|Cyclic Citrullinated Peptide (CCP) Antibody||Blood sample||The number of anti-CCP antibodies, used to rule out rheumatoid arthritis|
|Rheumatoid Factor (RF)||Blood sample||A protein produced by the immune system, used to rule out rheumatoid arthritis|
Imaging tests may be used to detect bone damage and other features consistent with gout but are often unnecessary if a diagnosis can be made based on a synovial fluid analysis. Rarely, the removal and microscopic examination of tissue around the joint, called a synovial tissue biopsy, may be used to rule out other causes of joint pain.
The American College of Rheumatology recommends that African American patients and patients of Southeast Asian descent receive HLA testing prior to starting certain medications that lower levels of uric acid in the body. HLA testing determines whether or not a patient has a HLA–B*5801 allele, or gene variant, that puts them at a higher risk of experiencing severe side effects from urate-lowering medications. HLA testing is not necessary for patients of other ethnic and racial backgrounds.
Getting Tested for Gout
Gout testing is ordered by a doctor or specialist when there are signs or symptoms consistent with gout. Gout testing may be performed during a flare of gout or based on a patient’s history of symptoms similar to gout.
A sample of synovial fluid can be obtained in a doctor’s office through a procedure called a joint aspiration or arthrocentesis. During a joint aspiration, a doctor uses a needle to withdraw a small sample of synovial fluid from the joint for analysis. If additional tests are needed to rule out other conditions, a blood sample can be drawn in a doctor’s office or other medical setting.
In some cases, uric acid testing may require a 24-hour urine sample. A 24-hour urine test requires that patients collect all of their urine produced over a 24-hour period.
At-home test kits may be available to analyze blood levels of uric acid. These kits involve obtaining a drop of blood from a finger stick, applying the blood sample to a test strip, and reading the level of uric acid on a handheld meter.
At-home testing does not diagnose gout and is not a substitute for either medical care or testing ordered by a doctor or rheumatologist.