Should urate levels be checked during an acute gout attack?

Checking Urate Levels During Acute Gout Attacks

Your provider is correct—serum urate levels should NOT be used to confirm or exclude gout during an acute attack, as they are frequently normal or even low during flares and can be misleading for diagnosis. 1

Why Urate Levels Are Unreliable During Acute Attacks

The American College of Physicians guidelines explicitly state that serum uric acid levels do not confirm or exclude gout during acute attacks because many patients have normal levels during flares, and hyperuricemia alone does not equal gout. 1

Key Evidence on Normal Urate During Attacks

• In the largest acute gout treatment trials to date, 14% of patients had truly normal serum urate (≤6 mg/dL) and 32% had levels ≤8 mg/dL during their acute attack. 2
• Approximately 40% of gout patients present with normouricemia during acute flares, particularly those who are post-surgical, on hemodialysis, or have preserved renal function. 3
• Attacks can still occur despite serum urate levels being below 6.8 mg/dL (the saturation point) due to persistence of tophi and an increased body uric acid pool. 2

Why This Happens Physiologically

• During acute inflammation, serum urate levels can drop temporarily as urate shifts into inflamed tissues or is consumed in the inflammatory process. 2
• Patients on chronic allopurinol are significantly more likely to have lower urate levels during acute attacks (mean 7.1 vs. 8.5 mg/dL in non-users), making the test even less useful. 2
• The presence of tissue crystal deposits (tophi) means attacks can occur even when serum levels appear "normal." 4

When Urate Levels ARE Useful

Serum urate monitoring is valuable for managing chronic gout and guiding urate-lowering therapy, but NOT for diagnosing acute attacks. 1

Appropriate Timing for Urate Testing

• Check baseline urate levels AFTER the acute attack has resolved to assess need for urate-lowering therapy. 1
• Monitor urate levels during chronic management to ensure therapeutic targets are achieved (<6 mg/dL for most patients, <5 mg/dL for severe disease with tophi). 5
• Patients achieving serum urate <6.0 mg/dL at 1 year have approximately 5% risk of acute attacks, versus 10-15% risk for those ≥6.0 mg/dL. 1

The Gold Standard for Diagnosis

Demonstration of monosodium urate crystals in synovial fluid or tophus aspirates permits definitive diagnosis of gout, not serum urate levels. 1

• A routine search for MSU crystals is recommended in all synovial fluid samples from undiagnosed inflamed joints. 1
• For typical presentations (recurrent podagra with hyperuricemia), clinical diagnosis alone is reasonably accurate but not definitive without crystal confirmation. 1

Common Pitfall to Avoid

The critical error is using a "normal" urate level during an acute attack to rule out gout—this can lead to missed diagnoses and delayed treatment. 5 The EULAR guidelines emphasize that while hyperuricemia is the most important risk factor for gout, serum levels during acute attacks are unreliable for diagnosis. 1

Clinical Bottom Line

• During acute attack: Diagnose based on clinical features and crystal identification if possible; do NOT rely on serum urate to confirm or exclude gout. 1
• After attack resolves: Check serum urate to guide long-term management decisions about urate-lowering therapy. 1
• During chronic management: Monitor urate levels to ensure therapeutic targets are met and adjust therapy accordingly. 1