What Is Gout?
Gout is a common form of arthritis, caused by high levels of uric acid in the blood. Uric acid is produced by the body during the breakdown of substances called purines. Purines are found in all body tissues and in many foods, such as red meat, organ meat, some types of seafood, dried beans, peas, asparagus, mushrooms, and beer.
The concentration of uric acid in the blood can rise when the body’s production of uric acid increases, a person eats foods high in purines, or the kidneys are unable to adequately eliminate uric acid. In people with gout, elevated levels of uric acid form needle-like urate crystals that build up around the joints and form deposits under the skin. The most frequently affected joint is the big toe, but gout can also affect joints in the hands, elbows, wrists, knees, ankles, and feet.
People with gout experience intense episodes, called flares, of inflammation, swelling, heat, and severe pain in the affected joints. Early in the disease, gout flares usually last a few days to several weeks. Over time, episodes occur more often and last longer as some people develop a chronic form of gout, called gouty arthritis.
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.
Sources and Resources
A.D.A.M. Medical Encyclopedia. Gout. Updated April 2, 2021. Accessed May 1, 2021. https://medlineplus.gov/ency/article/000422.htm
A.D.A.M. Medical Encyclopedia. Uric acid urine test. Updated April 2, 2021. Accessed May 1, 2021. https://medlineplus.gov/ency/article/003616.htm
A.D.A.M. Medical Encyclopedia. Uric acid – blood. Updated April 2, 2021. Accessed May 1, 2021. https://medlineplus.gov/ency/article/003476.htm
American College of Rheumatology. Gout. Updated March 2019. Accessed May 1, 2021. https://www.rheumatology.org/I-Am-A/Patient-Caregiver/Diseases-Conditions/Gout
ARUP Consult. Gout. Updated June 2020. Accessed May 1, 2021. https://arupconsult.com/content/hyperuricemia
Centers for Disease Control and Prevention. Gout. Updated July 27, 2020. Accessed May 1, 2021. https://www.cdc.gov/arthritis/basics/gout.html
FitzGerald JD, Dalbeth N, Mikuls T, et al. 2020 American College of Rheumatology Guideline for the Management of Gout [published correction appears in Arthritis Care Res (Hoboken). 2020 Aug;72(8):1187] [published correction appears in Arthritis Care Res (Hoboken). 2021 Mar;73(3):458]. Arthritis Care Res (Hoboken). 2020;72(6):744-760. doi:10.1002/acr.24180
Gaffo AL. Clinical manifestations and diagnosis of gout. In: Dalbeth N, ed. UpToDate. Updated December 1, 2019. Accessed May 1, 2021. https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-gout
Helgoff SM. Monoarthritis in adults: Etiology and evaluation. In: Shmerling RH, ed. UpToDate. Updated July 01, 2019. Accessed May 1, 2021. https://www.uptodate.com/contents/monoarthritis-in-adults-etiology-and-evaluation
Mandell BF. Gout. Merck Manuals Professional Edition. Updated October 2020. Accessed May 1, 2021. https://www.merckmanuals.com/professional/musculoskeletal-and-connective-tissue-disorders/crystal-induced-arthritides/gout
MedlinePlus: National Library of Medicine. Gout. Published March 17, 2016. Accessed May 1, 2021. https://medlineplus.gov/gout.html
MedlinePlus: National Library of Medicine. CCP antibody test. Updated July 30, 2020. Accessed May 1, 2021. https://medlineplus.gov/lab-tests/ccp-antibody-test/
MedlinePlus: National Library of Medicine. Erythrocyte sedimentation rate (ESR). Updated July 31, 2020. Accessed May 1, 2021. https://medlineplus.gov/lab-tests/erythrocyte-sedimentation-rate-esr/
MedlinePlus: National Library of Medicine. Complete blood count (CBC). Updated July 31, 2020. Accessed May 1, 2021. https://medlineplus.gov/lab-tests/complete-blood-count-cbc/
MedlinePlus: National Library of Medicine. Gram stain. Updated August 13, 2020. Accessed May 1, 2021. https://medlineplus.gov/lab-tests/gram-stain/
MedlinePlus: National Library of Medicine. Rheumatoid factor (RF) test. Updated December 3, 2020. Accessed May 1, 2021. https://medlineplus.gov/lab-tests/rheumatoid-factor-rf-test/
MedlinePlus: National Library of Medicine. Uric acid test. Updated December 10, 2020. Accessed May 1, 2021. https://medlineplus.gov/lab-tests/uric-acid-test/
MedlinePlus: National Library of Medicine. C-reactive protein (CRP) test. Updated March 3, 2021. Accessed December 3, 2020. https://medlineplus.gov/lab-tests/c-reactive-protein-crp-test/
MedlinePlus: National Library of Medicine. Synovial fluid analysis. Updated March 8, 2021. Accessed May 1, 2021. https://medlineplus.gov/lab-tests/synovial-fluid-analysis/
Merck Manual Editorial Staff. Gout. Merck Manual Quick Facts. Updated October 2019. Accessed May 1, 2021. https://www.merckmanuals.com/home/quick-facts-bone,-joint,-and-muscle-disorders/gout/gout
Merriman T. Pathophysiology of gout. In: Dalbeth N, ed. UpToDate. Updated July 14, 2020. Accessed May 1, 2021. https://www.uptodate.com/contents/pathophysiology-of-gout
Perez-Ruiz F. Patient education: Gout (beyond the basics). In: Dalbeth N, ed. UpToDate. Updated December 5, 2019. Accessed May 1, 2021. https://www.uptodate.com/contents/gout-beyond-the-basics
Perez-Ruiz F. Pharmacologic urate-lowering therapy and treatment of tophi in patients with gout. In: Dalbeth N, ed. UpToDate. Updated December 16, 2020. Accessed May 1, 2021. https://www.uptodate.com/contents/pharmacologic-urate-lowering-therapy-and-treatment-of-tophi-in-patients-with-gout
Shmerling RH. Evaluation of the adult with polyarticular pain. In: Helfgott, SM, ed. UpToDate. Updated March 5, 2021. Accessed May 1, 2021. https://www.uptodate.com/contents/evaluation-of-the-adult-with-polyarticular-pain