What are the diagnostic criteria and treatment options for gouty arthritis?

Diagnosis of Gouty Arthritis

The definitive diagnosis of gout requires identification of monosodium urate (MSU) crystals in synovial fluid or tophus aspirate using polarized light microscopy, which remains the gold standard with sensitivity and specificity approaching 100%. 1

Three-Step Diagnostic Algorithm

The European League Against Rheumatism recommends a hierarchical three-step approach for diagnosing gout 1:

Step 1: Synovial Fluid Analysis (Gold Standard)

• Joint aspiration with synovial fluid examination for MSU crystals is strongly recommended in any patient with undiagnosed inflammatory arthritis. 1
• MSU crystals appear as needle-shaped, negatively birefringent crystals under polarizing microscopy 2
• This test achieves sensitivity and specificity approaching 100% when performed by experienced operators 2, 3
• Even when MSU crystals are identified, Gram stain and culture must still be performed, as gout and septic arthritis can coexist. 2

Step 2: Clinical Diagnosis (When Crystal Analysis Not Feasible)

When joint aspiration cannot be performed or is declined, clinical diagnosis using validated algorithms achieves >80% sensitivity and specificity 3. The following features are highly suggestive of gout 1:

• Monoarticular involvement of the first metatarsophalangeal joint (podagra) 1, 2
• Rapid onset of severe pain and swelling reaching maximum intensity within 24 hours 1, 2
• Erythema over the affected joint 1, 2
• Previous similar acute arthritis episodes 1
• Male gender and associated cardiovascular diseases 1
• Hyperuricemia (though not diagnostic alone) 1, 2

The 2015 ACR/EULAR classification criteria (score ≥8 points) has sensitivity of 92% and specificity of 89% with imaging, or 85% sensitivity and 78% specificity without imaging. 4, 3 Key high-value features include presence of tophi (odds ratio 7.29) and resolution of pain within 2 weeks (odds ratio 3.58) 1, 4.

Step 3: Imaging (When Clinical Diagnosis Uncertain)

When clinical diagnosis is uncertain and crystal identification is not possible, imaging should be used to search for MSU crystal deposition 1:

Ultrasound (First-Line Imaging):

• The "double contour sign" on cartilage surfaces has sensitivity of 74% and specificity of 88% 2, 3
• Can detect tophi not evident on clinical examination 1, 2
• Performs better in late disease (>2 years duration) with 63% sensitivity compared to 50% in early disease 2
• Always include the first metatarsophalangeal joint in imaging, regardless of whether it is symptomatic 2

Dual-Energy CT (DECT):

• Sensitivity of 85-100% and specificity of 83-92% for detecting MSU crystal deposits 2, 3
• Most accurate in patients with disease duration >2 years 2, 3
• Preferred when comprehensive assessment of MSU crystal burden is needed 2

Plain Radiographs:

• Have limited value for diagnosing acute gout flares 1
• Useful only for assessing chronic structural damage in long-standing gout 2

Critical Diagnostic Pitfalls to Avoid

• Never diagnose gout based on hyperuricemia alone - specificity is only 53-61%, and only 22% of patients with serum uric acid >9 mg/dL develop gout over 5 years 1
• Conversely, absence of hyperuricemia has a markedly low likelihood ratio for gout, essentially ruling it out 1, 2
• Ultrasound sensitivity is significantly lower in early disease (<2 years), with only 50% sensitivity for double contour sign versus 63% in late disease 2
• When septic arthritis cannot be clinically excluded, joint aspiration with Gram stain and culture is mandatory regardless of gout suspicion 2
• Clinical algorithms have relatively low specificity, raising risk for missed diagnosis of septic arthritis, which has similar initial presentation 2

Risk Factor and Comorbidity Assessment

All patients with suspected or confirmed gout require systematic evaluation for: 1

• Chronic kidney disease 1
• Obesity 1
• Hypertension 1
• Ischemic heart disease 1
• Heart failure 1
• Diabetes 1
• Dyslipidemia 1

Evaluate for modifiable risk factors: 1

• Medications: diuretics, low-dose aspirin, cyclosporine, tacrolimus 1
• Alcohol consumption (particularly beer and spirits) 1
• Non-diet sodas and high-fructose corn syrup 1
• Diet high in meat and shellfish 1

When Clinical Diagnosis Alone Is Acceptable

For typical recurrent podagra with hyperuricemia, clinical diagnosis is reasonably accurate, particularly when the patient has documented history of crystal-proven gout. 2 Clinical diagnosis alone is acceptable when the patient has classic podagra presentation with rapid onset, no fever or systemic signs suggesting infection, and multiple characteristic risk factors present 2.