From the Guidelines
Gout testing should primarily involve joint aspiration to identify monosodium urate crystals, which is the gold standard for diagnosis, as recommended by the most recent and highest quality study 1. When gout is suspected, a healthcare provider should order a serum uric acid test, which typically shows elevated levels above 6.8 mg/dL, though normal levels don't rule out gout.
Key Points to Consider:
- Joint aspiration (arthrocentesis) provides definitive diagnosis by identifying needle-shaped, negatively birefringent crystals under polarized light microscopy.
- This procedure involves extracting fluid from an affected joint using a needle and syringe.
- Additional tests may include complete blood count, kidney function tests, and imaging studies like X-rays or ultrasound to assess joint damage or rule out other conditions.
- Testing is most accurate during an acute gout attack when crystals are abundant in the joint fluid.
- Patients should avoid taking urate-lowering medications before testing as this can affect results.
- Early and accurate diagnosis allows for appropriate treatment with medications like colchicine, NSAIDs, or corticosteroids for acute attacks, and allopurinol or febuxostat for long-term management to prevent recurrent attacks and joint damage.
Imaging Modalities:
- Ultrasound and DECT are both recommended imaging modalities for the diagnostic assessment of gout, as stated in the 2023 EULAR recommendations 1.
- The choice of technique should depend on the clinical scenario, in addition to availability and operator expertise.
- In general, early disease will warrant investigation with ultrasound rather than DECT, due to the capability of ultrasound to depict synovitis.
Clinical Diagnosis:
- Clinical algorithms can be used to diagnose gout, particularly when patients present with typical features such as podagra, as stated in the 2018 updated European League Against Rheumatism evidence-based recommendations 1.
- However, the specificity of these algorithms is not high enough to replace demonstration of MSU crystals in SF for the diagnosis of gout.
- The presence of hyperuricaemia alone is not sufficient to establish a diagnosis of gout, as it has a low specificity, ranging from 53% to 61% 1.
From the Research
Gout Testing Methods
- Gout is typically diagnosed using clinical criteria from the American College of Rheumatology 2
- Diagnosis may be confirmed by identification of monosodium urate crystals in synovial fluid of the affected joint 2
- Arthrocentesis should be performed when suspicion for an underlying septic joint is present; synovial fluid or tophus analysis should be performed if the diagnosis is uncertain 3
Clinical Prediction Rules
- Diagnosis of gout can be made using several validated clinical prediction rules 3
- Clinical criteria include swelling, pain, or tenderness in a peripheral joint or bursa, including the development of a tophus 3
Laboratory Tests
- No specific laboratory tests are mentioned in the provided studies as a primary method for diagnosing gout
- However, urate-lowering therapy is used to prevent flare-ups and reduce uric acid levels, which is key to avoiding gout flares 2, 4
Imaging Studies
- No specific imaging studies are mentioned in the provided studies as a primary method for diagnosing gout
- However, joint damage and chronic gouty arthritis are indications for long-term urate-lowering therapy 3