What is the initial workup for a patient with suspected gout?

Initial Workup for Suspected Gout

The definitive diagnosis of gout requires synovial fluid analysis to identify monosodium urate (MSU) crystals when clinical judgment indicates that diagnostic testing is necessary in patients with possible acute gout. 1

Clinical Assessment

When evaluating a patient with suspected gout, focus on these key clinical features:

• Joint involvement pattern:

  • First metatarsophalangeal (MTP) joint, ankle, or knee involvement 1
  • Monoarticular presentation (especially in early disease) 1
  • Rapid onset of severe pain and swelling (reaching maximum intensity within 24 hours) 1
  • Erythema over the affected joint 1

• History elements:

  • Previous similar acute arthritis episodes 1
  • Male gender 1
  • Associated cardiovascular diseases 1
  • Hyperuricemia 1

Diagnostic Algorithm

1. Synovial fluid analysis (first-line):

   • Perform joint aspiration and examine for MSU crystals using polarized light microscopy 1
   • This is particularly important when septic arthritis is in the differential diagnosis 1

2. When synovial fluid analysis is not feasible:

   • Apply validated clinical prediction rules such as:
     • Janssens diagnostic rule (sensitivity 73-96%, specificity 47-86%) 1
     • Clinical Gout Diagnosis criteria (sensitivity 97%, specificity 96%) 1
   • These incorporate features like male sex, previous arthritis attacks, onset within 1 day, joint redness, first MTP involvement, hypertension, and serum uric acid level 2

3. Laboratory tests:

   • Serum uric acid level (though diagnosis should not be made on hyperuricemia alone) 1, 3
   • Inflammatory markers (ESR, CRP) may be elevated but are nonspecific 4
   • Note: Normal serum uric acid levels do not exclude gout, as up to 63.3% of patients may have normal levels during acute attacks 4

4. Imaging studies (when diagnosis remains uncertain):

   • Ultrasound: Look for double contour sign (sensitivity 37-78%, specificity 64-97%) 1
   • Dual-energy CT (DECT): High sensitivity (85-100%) and specificity (83-92%) 1
   • Plain radiographs: Limited value for acute gout but may show erosions in chronic disease 1

Risk Factor Assessment

Always evaluate for risk factors and comorbidities:

• Chronic kidney disease 1, 3
• Obesity 1, 3
• Hypertension 1, 3
• Medications (diuretics, low-dose aspirin, cyclosporine, tacrolimus) 1
• Alcohol consumption (particularly beer and spirits) 1
• Diet rich in meat, shellfish, and fructose-rich foods/beverages 1, 5
• Ischemic heart disease, heart failure, diabetes, and dyslipidemia 1

Common Pitfalls to Avoid

• Do not diagnose gout based solely on hyperuricemia - this has poor sensitivity and specificity (53-61%) 1, 3
• Do not exclude gout based on normal serum uric acid - levels may be normal during acute attacks 4
• Do not miss septic arthritis - always consider joint aspiration when infection is possible 1
• Do not delay treatment - early intervention improves outcomes 3

Special Considerations

• For patients with early-onset gout (<2 years of symptoms), clinical algorithms may have lower sensitivity (58-71%) but higher specificity (84-92%) 1
• For patients with longer disease duration (>2 years), clinical algorithms have higher sensitivity (89-99%) but lower specificity (34-65%) 1
• DECT is less sensitive in patients with recent-onset acute gout 1

By following this systematic approach to the diagnosis of suspected gout, clinicians can make accurate diagnoses and initiate appropriate management to reduce morbidity and improve quality of life.