What are the diagnostic criteria for gout (gouty arthritis)?

From the Guidelines

Gout diagnosis should be based on a three-step approach, starting with the identification of monosodium urate (MSU) crystals in synovial fluid or tophus aspirates, followed by clinical diagnosis if crystal identification is not feasible, and finally, imaging studies such as ultrasound or dual-energy CT if a clinical diagnosis is uncertain. This approach is recommended by the European League Against Rheumatism (EULAR) [ 1 ]. The identification of MSU crystals is the gold standard for diagnosing gout, with a high sensitivity and specificity [ 1 ]. However, if synovial fluid analysis is not possible, a clinical diagnosis can be made based on the presence of hyperuricemia and associated clinical features of gout, such as podagra (gout flare at the first metatarsophalangeal joint) [ 1 ].

Diagnostic Tools

The following diagnostic tools can be used to diagnose gout:

• Synovial fluid analysis for MSU crystals
• Clinical diagnosis based on hyperuricemia and associated clinical features
• Imaging studies such as ultrasound or dual-energy CT

Clinical Presentation

Clinical presentation is also crucial for diagnosing gout, with patients typically experiencing:

• Sudden, severe joint pain (often in the first metatarsophalangeal joint)
• Redness, swelling, and warmth of the affected joint
• Elevated inflammatory markers like ESR and CRP

Imaging Studies

Imaging studies can support the diagnosis of gout, with:

• X-rays showing normal findings in early disease but potentially revealing punched-out erosions with overhanging edges in chronic gout
• Ultrasound detecting the "double contour" sign representing crystal deposition
• Dual-energy CT specifically identifying urate deposits [ 1 ].

Recommendation

The diagnosis of gout should not be made on the presence of hyperuricemia alone, as it has a low specificity for the diagnosis of gout [ 1 ]. Instead, a combination of clinical evaluation, laboratory tests, and imaging studies should be used to establish the diagnosis. The American College of Rheumatology/European League Against Rheumatism classification criteria can help establish the diagnosis when crystal analysis is not available [ 1 ]. Early and accurate diagnosis is essential for proper management to prevent joint damage and complications from chronic hyperuricemia.

From the FDA Drug Label

The mean age of study subjects was 55 years (23-89); 82% were male, mean body mass index (BMI) was 33 kg/m2, mean duration of gout was 15 years, and mean baseline SUA was 10 mg/dL Entry criteria for patients to be eligible for the trials were: baseline serum uric acid (SUA) of at least 8 mg/dL; had symptomatic gout with at least 3 gout flares in the previous 18 months or at least 1 gout tophus or gouty arthritis; and had a self-reported medical contraindication to allopurinol or medical history of failure to normalize uric acid (to less than 6 mg/dL) with at least 3 months of allopurinol treatment at the maximum medically appropriate dose.

The diagnosis of gout in the study subjects was based on the following criteria:

• Baseline serum uric acid (SUA) of at least 8 mg/dL
• Symptomatic gout with at least 3 gout flares in the previous 18 months
• At least 1 gout tophus or gouty arthritis
• Self-reported medical contraindication to allopurinol or medical history of failure to normalize uric acid with allopurinol treatment 2 2

From the Research

Diagnosis of Gout

• Gout is characterized by painful joint inflammation, most commonly in the first metatarsophalangeal joint, resulting from precipitation of monosodium urate crystals in a joint space 3.
• The diagnosis of gout can be made using clinical criteria from the American College of Rheumatology, and may be confirmed by identification of monosodium urate crystals in synovial fluid of the affected joint 3, 4, 5.
• Clinical presentation of gout typically includes rapid development of severe joint pain, swelling, and tenderness that reaches its maximum within 6-12 hours, especially with overlying erythema, most classically in the first metatarsophalangeal joint 4, 5.
• Risk factors for gout include male sex, obesity, hypertension, alcohol intake, diuretic use, a diet rich in meat and seafood, chronic kidney disease, and a diet heavy in fructose-rich food and beverages 6.

Diagnostic Criteria

• Demonstrating the presence of monosodium urate crystals in the joint fluid or tophus is the gold standard for the diagnosis of gout 4, 5.
• In the absence of demonstrating the presence of monosodium urate crystals, clinical, radiologic, and laboratory criteria are helpful in making the diagnosis of gout 4, 5.
• Several validated clinical prediction rules can be used to make the diagnosis of gout 6.
• Arthrocentesis should be performed when suspicion for an underlying septic joint is present, and synovial fluid or tophus analysis should be performed if the diagnosis is uncertain 6.

Laboratory and Radiologic Findings

• Laboratory findings for gout may include elevated uric acid levels, although this is not always present 3, 6.
• Radiologic findings for gout may include joint damage and the presence of tophi 6, 5.
• Synovial fluid analysis can confirm the presence of monosodium urate crystals, which is diagnostic of gout 3, 4, 5.