When is the best time to check uric acid levels in blood after a gout flare?

Best Time to Check Uric Acid After Gout Flare

Serum uric acid (SUA) should be checked during intercritical periods (between flares) rather than during an acute gout attack, as SUA levels are often falsely lowered during acute flares. 1

Why SUA Levels Are Unreliable During Acute Flares

Measuring SUA during an acute gout attack has significant limitations:

• SUA behaves as a negative acute phase reactant, becoming temporarily lowered during episodes of acute inflammation and stress 1
• Studies have shown that patients with gout have lower SUA levels (sometimes even within normal range) during acute attacks compared to intercritical periods 1
• The mechanism appears to be increased renal excretion of uric acid during acute episodes 1
• In a large clinical trial, 14% of patients had normal SUA levels (<6 mg/dL) during acute gout attacks, and 32% had levels ≤8 mg/dL 2

Optimal Timing for SUA Measurement

• Wait until the acute inflammation has completely resolved (typically 2-4 weeks after the flare subsides)
• Measure SUA during an intercritical period to get an accurate baseline
• This timing provides a more reliable assessment of the patient's true uric acid status

Clinical Implications

This timing issue has important implications for management:

• Do not exclude a diagnosis of gout based on normal SUA levels during an acute attack 3
• Do not make treatment decisions about urate-lowering therapy (ULT) based on SUA levels obtained during acute flares
• When monitoring ULT efficacy, always check SUA during intercritical periods

Treatment Target Considerations

When measuring SUA during intercritical periods:

• The target for ULT should be <6 mg/dL (360 μmol/L) 1
• This target is below the saturation point for monosodium urate (MSU) crystal formation (6.8 mg/dL) 4
• For patients with severe gout (tophi, chronic arthropathy, frequent attacks), a lower target of <5 mg/dL (300 μmol/L) may be appropriate until crystal dissolution occurs 1

Monitoring Protocol

For optimal management of gout:

• Measure baseline SUA during an intercritical period before starting ULT
• After initiating ULT, check SUA every 2-4 weeks during dose titration 1
• Once target is achieved, monitor periodically (every 6 months) to ensure continued control
• Remember that SUA should be maintained at target levels lifelong 1

Common Pitfalls to Avoid

• Misinterpreting normal SUA during an acute flare as evidence against gout diagnosis
• Starting or adjusting ULT based on SUA levels obtained during acute inflammation
• Failing to recognize that even with normal SUA during a flare, patients may have significant urate crystal burden in tissues
• Not considering that some patients may have modified their risk factors prior to presentation (e.g., stopped diuretics, reduced alcohol intake) 1

By measuring SUA during intercritical periods rather than during acute flares, clinicians can make more accurate diagnostic and therapeutic decisions for patients with gout.