Gout Diagnosis Guidelines

Diagnostic Approach

The European League Against Rheumatism recommends that demonstration of monosodium urate (MSU) crystals in synovial fluid permits definitive diagnosis of gout with the highest strength of recommendation (96, 95% CI 93-100) 1, 2, 3
The American College of Rheumatology suggests that a routine search for MSU crystals is recommended in all synovial fluid samples obtained from undiagnosed inflamed joints (strength of recommendation 90, 95% CI 83-97) 1, 2, 3
Crystal identification from asymptomatic joints during intercritical periods allows definite diagnosis (strength of recommendation 84, 95% CI 78-91) 1, 2, 3

The European League Against Rheumatism states that serum uric acid levels do not confirm or exclude gout, as many people with hyperuricemia never develop gout, and patients with crystal-proven gout may have normal serum levels during acute attacks 1, 2, 3, 4
Serum uric acid behaves as a negative acute phase reactant, temporarily decreasing during acute inflammation 4

The American College of Rheumatology recommends that gout and septic arthritis may coexist, so Gram stain and culture should still be performed even if MSU crystals are identified when infection is suspected (strength of recommendation 93, 95% CI 87-99) 1, 2, 3

The European League Against Rheumatism suggests aspirating the joint and examining for MSU crystals under polarized light microscopy—this is the definitive diagnostic test 1, 2, 3
The American College of Rheumatology recommends not relying on serum uric acid levels alone for diagnosis, as they have limited diagnostic value especially during acute attacks 1, 2, 3, 4

Serum uric acid and serum urate are the same measurement, as uric acid exists predominantly as urate at physiologic pH, so laboratories may use either term interchangeably, according to the European League Against Rheumatism 5, 6
Most clinical laboratories in the United States report this test as "serum uric acid" or "uric acid, serum," so ordering "uric acid" will be universally understood, as recommended by the American College of Rheumatology 5, 6

The treatment target is serum uric acid <6 mg/dL (360 μmol/L), and <5 mg/dL (300 μmol/L) in severe gout with tophi, as suggested by the European League Against Rheumatism 5, 6
Monitor serum uric acid levels regularly while titrating urate-lowering therapy to achieve and maintain target levels, according to the American College of Rheumatology 5, 7