From the Guidelines
To diagnose gout as a primary care physician, I strongly recommend using synovial fluid analysis when clinical judgment indicates that diagnostic testing is necessary, as it is the gold standard for confirming the presence of monosodium urate crystals, which is essential for diagnosing gout. This approach is supported by the American College of Physicians (ACP) guideline, which suggests that clinicians use synovial fluid analysis for diagnosing acute gout when necessary 1.
When evaluating a patient for gout, it is crucial to start with a comprehensive clinical assessment, including a detailed history and physical examination. Key features to look for include sudden onset of intense joint pain, typically affecting the first metatarsophalangeal joint, though other joints may be involved. Look for erythema, swelling, and warmth over the affected joint. Obtain a detailed history including previous attacks, family history, dietary habits, alcohol consumption, and medication use.
Laboratory testing should include serum uric acid levels, though normal levels don't exclude gout during an acute attack. Joint aspiration with synovial fluid analysis is the most accurate diagnostic test - the presence of negatively birefringent monosodium urate crystals under polarized microscopy confirms gout 1. Consider complete blood count, renal function tests, and inflammatory markers to assess overall health and rule out other conditions.
Imaging studies such as X-rays may show normal findings in early gout but can reveal punched-out erosions with overhanging edges in chronic cases. Ultrasound can detect tophi and the "double contour" sign of urate crystal deposition. When joint aspiration isn't feasible, diagnosis may rely on clinical criteria such as the American College of Rheumatology/European League Against Rheumatism classification criteria, which considers pattern of joint involvement, characteristics and timing of symptoms, and laboratory findings.
Key points to consider in the diagnosis of gout include:
- Clinical presentation: sudden onset of intense joint pain, erythema, swelling, and warmth
- Laboratory testing: serum uric acid levels, joint aspiration with synovial fluid analysis
- Imaging: X-rays, ultrasound
- Clinical criteria: American College of Rheumatology/European League Against Rheumatism classification criteria
- Risk factors: male sex, overweight or obesity, hypertension, excess alcohol intake, diuretic use, diet rich in meat and seafood, poor kidney function 1.
From the Research
Diagnosis of Gout
To diagnose gout, the following methods can be used:
- Clinical criteria from the American College of Rheumatology 2
- Identification of monosodium urate crystals in synovial fluid of the affected joint 2, 3, 4, 5
- Validated clinical prediction rules 5
- Arthrocentesis to rule out septic joint 5
- Synovial fluid or tophus analysis if diagnosis is uncertain 5
Clinical Presentation
Gout is characterized by:
- Painful joint inflammation, most commonly in the first metatarsophalangeal joint 2, 3
- Swelling, pain, or tenderness in a peripheral joint or bursa 5
- Development of a tophus 5
- Acute gout flares can be monoarticular or polyarticular, involving lower extremity joints 3
Risk Factors
Risk factors for gout include:
- Obesity 3, 5
- High alcohol and purine-rich food consumption 2, 3, 5
- Use of diuretics 2, 3, 5
- Male sex 5
- Hypertension 5
- Chronic kidney disease 5
- Diet rich in meat and seafood 5
- Diet heavy in fructose-rich food and beverages 5
- Membership in certain ethnic groups, including Taiwanese, Pacific Islander, and New Zealand Maori 5
- Living in high-income countries 5