Diagnosis and Treatment of Gout

Diagnosis

• The American College of Rheumatology recommends that the definitive diagnosis of gout requires the identification of monosodium urate (MSU) crystals in synovial fluid or aspirated from tophi, which is the reference standard for diagnosis 1, 2
• The European League Against Rheumatism suggests that synovial fluid analysis should be performed in any patient with undiagnosed inflammatory arthritis, and requires a polarizing microscope and a trained operator to identify characteristic needle-shaped crystals with negative birefringence 1, 3
• Clinical diagnosis can be made when crystal analysis is not possible, based on suggestive clinical characteristics such as maximal joint inflammation within 24 hours, erythema over the affected joint, involvement of the first metatarsophalangeal joint (podagra), male sex, associated cardiovascular diseases, and hyperuricemia 1, 2

Imaging Studies

• Ultrasonography has high specificity for urate deposits, detects the "double contour" sign on cartilaginous surfaces, and identifies non-clinically evident tophi, with a sensitivity of 37-100% and specificity of 68-97% 1, 4, 5
• Dual-energy computed tomography (DECT) allows for non-invasive detection of MSU crystal deposits, with a sensitivity of 85-100% and specificity of 83-92% 4, 5

Risk Factors

• The American Heart Association recommends evaluating risk factors such as chronic kidney disease, overweight/obesity, medications (diuretics, low-dose aspirin, cyclosporine, tacrolimus), excessive alcohol consumption, consumption of non-diet soft drinks, and consumption of meats and seafood 1, 2

Comorbidities

• The European League Against Rheumatism suggests systematic evaluation of comorbidities in patients with gout, including obesity, dislipidemia, and other conditions 1, 2

Treatment

Acute Gout Attack

• The American College of Rheumatology recommends first-line treatment for acute gout, including low-dose colchicine, nonsteroidal anti-inflammatory drugs (NSAIDs), and/or glucocorticoids, depending on comorbidities and risk of adverse effects 6
• Colchicine is more effective than placebo and as effective as high-dose colchicine, but with a better safety profile, at a dose of up to 2 mg daily 2, 6
• NSAIDs should be started as soon as possible, and are contraindicated in patients with renal disease, peptic ulcer, or high cardiovascular risk 6

Long-term Treatment

• The European League Against Rheumatism recommends initiating hypouricemic treatment with allopurinol as first-line, starting with low doses and gradually increasing to achieve a target serum uric acid level below 0.36 mmol/L (6 mg/dL) 6
• Alternative treatments include uricosurics (benzbromarone, probenecid) or febuxostat, and uricase in severe cases where other therapies have failed or are contraindicated 6

Lifestyle Modifications

• The American Heart Association recommends advising patients on a healthy lifestyle, including weight loss, regular exercise, smoking cessation, avoidance of excessive alcohol consumption, and a diet low in purine-rich foods and high in vegetables and low-fat dairy products 4, 6

Follow-up

• Monitoring should include serum uric acid level, frequency of gout attacks, and size of tophi 4, 6

Special Considerations

Patients with Renal Insufficiency

• Allopurinol can be used in mild to moderate renal insufficiency, starting with low doses (50-100 mg) and monitoring for adverse events, while febuxostat and benzbromarone are alternative options that do not require dose adjustment 6

Tophi Treatment

• Tophi should be treated medically through sustained reduction of serum uric acid, preferably below 0.30 mmol/L (5 mg/dL), and surgery is only indicated in selected cases (nerve compression, mechanical impairment, or infection) 6

Asymptomatic Hyperuricemia

• The European League Against Rheumatism does not recommend pharmacological treatment of asymptomatic hyperuricemia to prevent gouty arthritis, renal disease, or cardiovascular events 6

Gout Diagnosis and Management

Clinical Diagnosis

• The American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) recommend using validated clinical prediction algorithms, such as the 2015 ACR/EULAR classification criteria, which demonstrate sensitivities of 84-99% and specificities of 66-96% for diagnosing gout 7, 8, 9
• The 2015 ACR/EULAR classification criteria have a score ≥8 points that is diagnostic for gout, with a sensitivity of 92% and specificity of 89% with imaging, and 85% sensitivity and 78% specificity without imaging 9
• Key high-value clinical features for diagnosing gout include the presence of tophi (odds ratio 7.29) 10 and resolution of pain within 2 weeks (odds ratio 3.58) 10

Imaging Studies

• Dual-Energy Computed Tomography (DECT) is the most accurate imaging modality for non-invasive detection of MSU crystal deposits, with sensitivity of 85-100% and specificity of 83-92% 9, 11
• Ultrasonography has high specificity for urate deposits and can detect subclinical disease, with the "double contour" sign on cartilaginous surfaces being the most specific finding (pooled sensitivity 74%, specificity 88%) 11

Diagnostic Algorithm

• The ACR/EULAR recommend attempting synovial fluid aspiration as the reference standard for diagnosing gout, especially if septic arthritis is in the differential 9
• If aspiration is not possible or negative, apply the 2015 ACR/EULAR classification criteria (score ≥8 diagnostic) 9
• In early disease (<2 years), consider Janssens diagnostic rule for higher sensitivity 9
• Consider advanced imaging, such as DECT or ultrasonography, if diagnosis remains uncertain 9, 11