What are the laboratory tests and management options for gout?

Laboratory Tests and Management Options for Gout

The gold standard for diagnosing gout is synovial fluid analysis with identification of monosodium urate (MSU) crystals using polarizing microscopy, while management includes NSAIDs, colchicine, or corticosteroids for acute flares and urate-lowering therapy with allopurinol as first-line treatment for chronic gout. 1, 2

Diagnostic Laboratory Tests

Gold Standard Test

• Synovial fluid aspiration and analysis using polarizing microscopy to identify MSU crystals is the reference standard for gout diagnosis, with sensitivity and specificity of 85-100% and 83-92%, respectively 2
• The presence of MSU crystals in synovial fluid is sufficient for diagnosing gout 1
• Joint aspiration may be technically difficult, especially in smaller joints, and can be painful for patients 1, 2

Alternative Diagnostic Methods

• Serum uric acid analysis, though commonly performed, has limited diagnostic utility as a stand-alone test since many patients with hyperuricemia never develop gout 1
• Dual-Energy Computed Tomography (DECT) shows sensitivities of 85-100% and specificities of 83-92% for diagnosing gout 2
• Ultrasonography demonstrates sensitivities of 37-100% and specificities of 68-97%, depending on the signs assessed 2
• Clinical prediction tools have demonstrated sensitivities and specificities greater than 80% compared to synovial fluid MSU crystal analysis 2

Management of Acute Gout Flares

First-Line Treatments

• Treatment should be initiated as early as possible for optimal outcomes 1, 3
• NSAIDs at full anti-inflammatory doses are effective when started promptly but should be avoided in patients with renal disease, heart failure, or cirrhosis 3
• Colchicine is most effective when started within 12 hours of symptom onset, with a low-dose regimen of 1.2 mg followed by 0.6 mg one hour later 1, 3
• Corticosteroids (oral prednisone 30-35 mg/day for 3-5 days) are recommended as first-line therapy in patients without contraindications 1, 3
• Intra-articular corticosteroid injection is recommended for single joint involvement 1

Long-Term Management

Urate-Lowering Therapy (ULT)

• ULT is indicated for patients with recurrent gout flares (≥2 per year), tophi, urate arthropathy, or renal stones 1, 3
• The treatment target is serum urate below 6 mg/dL (0.36 mmol/L), and eventually below 5 mg/dL (0.30 mmol/L) in patients with tophi 1, 4
• Allopurinol is the first-line ULT, starting at a low dose (100 mg/day) and gradually increasing every 2-4 weeks to achieve target serum urate levels 3, 5
• For patients with renal impairment, allopurinol dosing should be adjusted: with creatinine clearance of 10-20 mL/min, a daily dosage of 200 mg is suitable; with clearance <10 mL/min, daily dosage should not exceed 100 mg 5

Prophylaxis During ULT Initiation

• Prophylaxis with low-dose colchicine (0.5-1 mg/day) or low-dose NSAIDs is essential when starting ULT to prevent acute flares 1, 3
• Prophylaxis should be continued for at least 6 months after initiating ULT 1, 3
• In patients with renal impairment, colchicine dose should be reduced 1, 3

Monitoring and Follow-up

• Regular monitoring of serum urate levels is recommended to ensure target levels are achieved and maintained 1, 5
• The correct dosage for maintaining serum uric acid within normal range is best determined by using serum uric acid as an index 5
• In patients with pre-existing liver disease, periodic liver function tests are recommended during early stages of therapy 5
• For patients with decreased renal function, periodic assessment of renal function (BUN, serum creatinine, or creatinine clearance) should be performed 5

Special Considerations

• Patients with decreased renal function require lower doses of allopurinol than those with normal renal function 5
• Lifestyle modifications, including weight loss for overweight/obese patients, limiting alcohol intake (especially beer and spirits), and reducing intake of sugar-sweetened beverages are recommended 1, 3
• Regular screening for associated comorbidities (coronary heart disease, heart failure, stroke, diabetes) is recommended 1, 3

Common Pitfalls to Avoid

• Relying solely on serum uric acid for diagnosis, as hyperuricemia alone is insufficient to establish a diagnosis of gout 1, 2
• Initiating ULT during an acute attack, which can worsen symptoms 1
• Failing to provide prophylaxis when starting ULT, leading to increased risk of flares 1, 3
• Inadequate dosing of ULT, resulting in failure to achieve target serum urate levels 5, 4
• Discontinuing ULT prematurely, which can lead to recurrence of gout attacks 1, 4