From the Guidelines
Assessing gout requires a comprehensive approach that prioritizes joint fluid aspiration for crystal identification, supported by clinical evaluation, laboratory tests, and imaging studies, as recommended by the 2020 European League Against Rheumatism evidence-based guidelines 1. When evaluating a patient for gout, it is essential to start with a detailed history, focusing on sudden-onset joint pain, particularly in the big toe, ankles, or knees, along with redness, swelling, and warmth. The patient's history should also include questions about previous attacks, family history, diet, alcohol consumption, and medications that may affect uric acid levels.
Key Diagnostic Steps
- Measure serum uric acid levels, though these may be normal during acute attacks, with levels above 6.8 mg/dL supporting the diagnosis.
- Joint fluid aspiration is the gold standard diagnostic test, where polarized microscopy reveals negatively birefringent monosodium urate crystals, as emphasized by the American College of Physicians guideline 1.
- Complete blood count and inflammatory markers like ESR and CRP help assess inflammation severity.
- Imaging studies such as X-rays may show normal findings in early disease but can reveal erosions with overhanging edges ("rat-bite erosions") in chronic gout.
- Ultrasound can detect the "double contour sign" of urate crystal deposition, while dual-energy CT can specifically identify urate deposits, as recommended by the 2020 European League Against Rheumatism guidelines 1.
Differential Diagnosis
Differential diagnosis should rule out septic arthritis, pseudogout, and other inflammatory arthritides. The definitive diagnosis relies on crystal identification in joint fluid, but a combination of clinical presentation, laboratory findings, and imaging can strongly support the diagnosis when aspiration isn't feasible.
Risk Factors and Comorbidities
It is also crucial to search for risk factors for chronic hyperuricaemia, including chronic kidney disease, overweight, certain medications, and consumption of excess alcohol or specific foods, as well as to systematically assess for associated comorbidities such as obesity, renal impairment, hypertension, and diabetes, as recommended by the 2020 guidelines 1.
From the FDA Drug Label
The co-primary endpoints were: (i) patient’s assessment of gout flare pain intensity at the most affected joint at 72 hours post-dose measured on a 0-100 mm visual analogue scale (VAS) and (ii) the time to first new gout flare. Pain intensity at the most affected joint, assessed on a 0-100 mm VAS at 72-hours post-dose was the primary endpoint, and time to first new gout flare was a secondary endpoint.
To assess gout, pain intensity at the most affected joint can be measured using a 0-100 mm visual analogue scale (VAS) at 72 hours post-dose. Additionally, the time to first new gout flare can be assessed as a secondary endpoint.
- Key assessment tools:
- Patient’s assessment of gout flare pain intensity
- Time to first new gout flare 2
From the Research
Assessment of Gout
To assess gout, the following methods can be used:
- Synovial fluid aspiration and analysis, which is the gold standard for making the diagnosis of gout 3
- A presumptive (or clinical) diagnosis of gout may be made in consultation with published recommendations and criteria from expert societies when joint aspiration cannot be performed 3
- A thorough patient history and physical examination are critical to a presumptive diagnosis of gout 3
- Serum urate measurement at the time of an acute attack and at follow-up 2 weeks later can also be used to assess gout 3
Diagnostic Criteria
The diagnostic criteria for gout include:
- The presence of monosodium urate crystals in the synovial fluid 4, 5, 6
- A history of acute inflammatory arthritis 4, 5, 6
- The presence of tophaceous deposits 5
- Elevated serum urate levels 4, 5, 6
Treatment Guidance
Treatment of gout is guided by various major international societies, and includes:
- Standard pharmacotherapies for gout flares, such as colchicine, NSAIDs, and oral or intramuscular corticosteroids 4, 5, 6
- Urate-lowering therapies, such as allopurinol and febuxostat, to prevent gout flares 4, 5, 6
- Emerging therapies, such as IL-1 inhibitors and novel uricosurics, for refractory gout 4, 5