What is the initial workup for gout?

Initial Workup for Gout

The initial workup for gout should include synovial fluid analysis for monosodium urate (MSU) crystals as the gold standard for diagnosis, along with clinical evaluation using validated diagnostic criteria, and serum uric acid measurement. 1

Diagnostic Approach

Definitive Diagnosis

• Synovial fluid analysis for MSU crystals is the gold standard for diagnosis and should be performed whenever possible to confirm gout 1
• The presence of MSU crystals or tophi is considered diagnostic by itself 1

Clinical Diagnostic Criteria

When synovial fluid analysis is not feasible, several validated diagnostic algorithms can be used:

• Janssens diagnostic rule (Netherlands criteria): A 7-item algorithm with high diagnostic accuracy

  • Scores >8 have a positive predictive value of 87%
  • Scores <4 have a negative predictive value of 95%
  • More accurate in recent-onset symptoms (sensitivity 73-88%, specificity 75-86%) 1

• American College of Rheumatology (ACR) criteria: Requires 6 or more positive criteria out of 12 clinical signs

  • Sensitivity 70-92% and specificity 53-92% compared to MSU crystal analysis
  • Less accurate in early disease, more accurate in established gout 1

Key Clinical Features to Evaluate

• Monoarticular arthritis, typically affecting the first metatarsophalangeal joint
• Rapid onset of severe pain, erythema, and swelling
• History of previous similar attacks
• Asymmetric joint involvement
• Resolution of symptoms within 1-2 weeks without treatment
• Presence of tophi (if present, diagnostic) 1

Laboratory and Imaging Studies

Essential Laboratory Tests

• Serum uric acid level: While elevated levels support the diagnosis, normal levels do not exclude gout, especially during acute attacks 1
• Renal function tests: Important for treatment decisions and to assess for comorbid kidney disease 1
• Complete blood count and inflammatory markers (ESR, CRP): To assess inflammation and rule out infection 1

Imaging Studies

• Plain radiographs: May show normal findings in early disease but can reveal erosions with overhanging edges in chronic gout 1
• Ultrasound: Can detect MSU crystal deposits and the "double contour" sign (hyperechoic band over the articular cartilage) 1
• Dual-energy CT: Highly specific for detecting MSU crystal deposits, particularly useful for diagnosing tophaceous gout 1

Risk Factor Assessment

Modifiable Risk Factors

• Diet: High intake of purine-rich foods (organ meats, shellfish), alcohol (especially beer), and beverages sweetened with high-fructose corn syrup 2
• Medications: Loop and thiazide diuretics can increase uric acid levels 2
• Obesity 2
• Comorbidities: Hypertension, diabetes, chronic kidney disease 1

Non-modifiable Risk Factors

• Age and sex: More common in men and postmenopausal women 2
• Family history 2

Common Pitfalls and Caveats

• Misdiagnosis: Gout is often confused with other forms of inflammatory arthritis, particularly calcium pyrophosphate deposition disease (pseudogout) 1
• Relying solely on serum uric acid levels: Normal serum uric acid levels do not exclude gout, especially during acute attacks 1
• Failure to distinguish between acute management and chronic prevention: These require different therapeutic approaches 3
• Inadequate assessment of renal function: Critical for medication selection and dosing, especially for allopurinol 1, 4

Treatment Considerations Based on Diagnosis

Acute Flare Management

• First-line options: NSAIDs, colchicine (within 12 hours of flare onset), or oral corticosteroids 1
• Colchicine dosing: Loading dose of 1 mg followed 1 hour later by 0.5 mg on day 1 1
• Avoid colchicine in patients with severe renal impairment or those receiving strong P-glycoprotein/CYP3A4 inhibitors 1, 4

Urate-Lowering Therapy (ULT) Indications

• Strongly recommended for patients with:

  • One or more subcutaneous tophi
  • Radiographic damage attributable to gout
  • Frequent gout flares (≥2 annually) 1

• Conditionally recommended for patients with:

  • Previous flares but infrequent (<2/year)
  • First flare with comorbid moderate-to-severe CKD, serum urate >9 mg/dL, or urolithiasis 1

• Conditionally recommended against for:

  • First-time gout flare without complications
  • Asymptomatic hyperuricemia 1

When initiating ULT, allopurinol is the preferred first-line agent, started at a low dose with subsequent titration to achieve target serum urate levels <6 mg/dL 1.