Can a patient with a normal Bone Ultrasound Attenuation (BUA) result still experience gouty arthritis flares?

Can Normal Serum Uric Acid Still Present with Gout Flares?

Yes, patients can absolutely experience acute gouty arthritis flares despite having normal serum uric acid levels at the time of the attack—this occurs in approximately 10% of acute gout presentations because uric acid behaves as a negative acute phase reactant during inflammation. 1

Why Normal Uric Acid Doesn't Exclude Gout

• Serum uric acid drops during acute inflammation, making it an unreliable diagnostic marker during active flares, with only 53-61% sensitivity for gout diagnosis when measured during an attack 1
• Hyperuricemia has limited diagnostic value during acute episodes but remains essential for long-term management decisions 1
• The 2024 EULAR guidelines explicitly state that normal uric acid levels do not rule out gout in the appropriate clinical context 2, 1

Gold Standard Diagnosis Remains Crystal Analysis

• Joint aspiration with polarized light microscopy identifying monosodium urate (MSU) crystals is the definitive diagnostic test, with sensitivity of 84% and specificity approaching 100% 1
• MSU crystals appear as needle-shaped, negatively birefringent crystals under polarizing microscopy 2, 1
• Synovial fluid can detect MSU crystals in approximately 70% of patients with known gout even during intercritical periods, demonstrating that crystal deposition persists regardless of serum uric acid levels 1

When Imaging Can Replace Aspiration

• When characteristic ultrasound features (double contour sign or tophi) or dual-energy CT findings are identified, synovial fluid analysis is not needed to confirm gout, according to 2023 EULAR recommendations 2, 3
• Ultrasound has pooled sensitivity of 74% and specificity of 88% for the double contour sign, which represents MSU crystal deposition on cartilage surfaces 2, 3
• Dual-energy CT demonstrates 85-100% sensitivity and 83-92% specificity for detecting MSU crystal deposits 2, 1

Clinical Features That Support Gout Despite Normal Uric Acid

• Rapid onset of severe pain reaching maximum intensity within 6-12 hours strongly suggests gout over other conditions 1, 4
• Podagra (first metatarsophalangeal joint involvement) has the highest predictive value with odds ratio of 7.29 for gout diagnosis 4
• Resolution within 2 weeks even without treatment favors gout 4
• History of recurrent similar attacks is highly suggestive of gout 1

Critical Pitfall to Avoid

• Never exclude gout based solely on normal serum uric acid levels during an acute attack—this is a common diagnostic error that can lead to missed diagnosis and delayed treatment 1
• Always attempt joint aspiration when feasible, especially to rule out septic arthritis, which can coexist with gout 2, 1
• Gram stain and culture must be performed even when MSU crystals are identified because gout and septic arthritis can coexist 1

Practical Diagnostic Algorithm

1. If joint aspiration is feasible: Perform arthrocentesis with crystal analysis, Gram stain, and culture—this remains the gold standard 1

2. If aspiration is not feasible or unsuccessful: Use ultrasound as first-line imaging to identify double contour sign or tophi, always including the first metatarsophalangeal joint bilaterally even if asymptomatic 1, 3

3. If ultrasound is unavailable or equivocal: Consider dual-energy CT, particularly in patients with disease duration >2 years 1

4. For typical recurrent podagra with characteristic rapid onset: Clinical diagnosis has 95% strength of recommendation when combined with imaging findings, even with normal uric acid 1

Treatment Implications

• Do not delay anti-inflammatory treatment while awaiting definitive diagnosis in patients with classic presentation 2
• Measure serum uric acid for baseline, but recognize its limited diagnostic utility during acute attacks 1
• Recheck serum uric acid 2-4 weeks after the acute flare resolves to assess true baseline hyperuricemia and guide urate-lowering therapy decisions 1