How to diagnose and treat suspected gout in a patient with foot pain?

Diagnosis and Management of Suspected Gout in a 75-Year-Old Male with Foot Pain

You should perform joint aspiration with synovial fluid analysis for monosodium urate (MSU) crystals to definitively diagnose gout, as this is the gold standard and is recommended for every patient with suspected gout. 1

Diagnostic Approach: A Stepped Algorithm

Step 1: Joint Aspiration for Crystal Identification (Preferred)

• Synovial fluid aspiration and polarized light microscopy is the definitive diagnostic test and should be attempted in all cases of undiagnosed inflammatory arthritis, with the highest level of agreement among experts (8.8±0.3). 1, 2

• MSU crystals appear needle-shaped with strong negative birefringence under polarized microscopy, providing sensitivity of 63-78% and specificity of 93-100% when performed by experienced operators. 1, 2

• Joint aspiration is particularly critical to rule out septic arthritis, which can coexist with gout and cannot be reliably excluded by clinical algorithms alone. 2

• The procedure carries minimal risk: severe complications occur in only 0.1% of cases, with mild pain being the most common adverse effect (1.4% of cases). 2

Step 2: Clinical Diagnosis (If Joint Aspiration Not Feasible)

If joint aspiration cannot be performed, a clinical diagnosis is supported by these highly suggestive features: 1

• Monoarticular involvement of the foot (especially first metatarsophalangeal joint/podagra) or ankle joint
• Rapid onset of severe pain and swelling reaching maximum intensity within 6-24 hours 1
• Erythema overlying the affected joint
• Previous similar acute episodes of arthritis
• Male gender (relative risk 7.64) 1
• Associated cardiovascular comorbidities and hyperuricemia

Important caveat: These clinical features have high sensitivity (98%) but very low specificity (23%), meaning they can suggest gout but cannot definitively confirm it without crystal identification. 1

Step 3: Imaging (If Clinical Diagnosis Uncertain and Crystal Identification Not Possible)

When both joint aspiration and clinical certainty are lacking: 1

• Ultrasound is the preferred initial imaging modality, looking for:

  • "Double contour sign" at cartilage surfaces (pooled sensitivity 74%, specificity 88%) - highly specific for urate deposits 1, 2, 3
  • Tophi not evident on clinical examination 1

• Dual-energy CT (DECT) has sensitivity of 85-100% and specificity of 83-92%, but is less sensitive for early gout. 2, 3

• Plain radiographs have limited value for diagnosing acute gout flares but may show chronic changes. 1

Critical Diagnostic Pitfalls to Avoid

Do NOT Diagnose Gout Based on Hyperuricemia Alone

• Serum uric acid measurement alone cannot diagnose gout (expert agreement 8.9±0.2). 1

• Many patients with hyperuricemia never develop gout, and conversely, acute gout attacks can occur with normal serum uric acid levels during the flare. 2, 3

• Hyperuricemia is a risk factor, not a diagnostic criterion. 1

Always Consider Septic Arthritis

• Clinical algorithms cannot reliably rule out septic arthritis, which can coexist with gout. 2

• If there is any suspicion of infection (fever, immunosuppression, recent joint instrumentation), joint aspiration for Gram stain and culture is mandatory. 2

Essential Comorbidity Assessment

Once gout is diagnosed, systematically assess for: 1

• Renal function (chronic kidney disease increases risk 4.95-fold) 1
• Cardiovascular risk factors: hypertension (RR 3.93), coronary heart disease (RR 1.75), diabetes (RR 1.11) 1
• Obesity (RR 3.81) 1
• Medications: diuretics (RR 1.72), low-dose aspirin 1
• Dyslipidemia and metabolic syndrome 1

Risk Factors to Elicit in History

Document these modifiable risk factors: 1

• Alcohol consumption (particularly beer and spirits) - 17% increased risk per 10g daily 1
• Diet: meat consumption (RR 1.41), seafood (RR 1.51), sugar-sweetened beverages 1
• Diuretic use 1

Treatment Considerations (Brief Overview)

For acute gout flare treatment: 1

• Low-dose colchicine (up to 2 mg daily), NSAIDs, or glucocorticoids (intra-articular, oral, or intramuscular) depending on comorbidities
• Choice depends on renal function, cardiovascular disease, and gastrointestinal risk factors 1

In this 75-year-old patient, the priority is establishing a definitive diagnosis through joint aspiration before initiating treatment, unless septic arthritis is suspected (in which case aspiration becomes emergent). 1, 2