For which patients is a uric acid test recommended?

Uric Acid Testing: Recommended Patient Populations

Serum uric acid testing is recommended for patients with suspected or confirmed gout to guide urate-lowering therapy, but it should NOT be used as a standalone diagnostic test for gout, as levels can be normal during acute attacks and many people with hyperuricemia never develop gout. 1

Primary Indications for Serum Uric Acid Testing

Patients with Established Gout on Urate-Lowering Therapy

• Monitor serum uric acid every 2-5 weeks during dose titration of urate-lowering therapy until target levels (<6 mg/dL) are achieved 2, 3
• Check levels every 6 months once at target to ensure maintenance of therapeutic goals 2, 4
• The target is <6 mg/dL for most patients, or <5 mg/dL for those with severe gout (tophi, chronic arthropathy, frequent attacks) 2, 5

Patients Being Evaluated for Gout (With Important Caveats)

• Serum uric acid has limited diagnostic value during acute gout attacks because it behaves as a negative acute phase reactant and can be misleadingly normal or low during inflammation 1, 4
• Approximately 10% of patients with crystal-proven gout have serum uric acid <6 mg/dL during flares 4
• For diagnostic purposes, measure serum uric acid during intercritical periods (between attacks) rather than during acute flares 4
• Hyperuricemia (>7 mg/dL in men, >6 mg/dL in women) has only 57% sensitivity but 92% specificity for clinical gout 4

Patients with Typical Gout Presentations

• For typical presentations such as recurrent podagra with hyperuricemia, clinical diagnosis is reasonably accurate but not definitive without crystal confirmation 1
• Crystal demonstration in synovial fluid or tophus aspirates remains the gold standard for definitive gout diagnosis (strength of recommendation: 96) 1

Special Populations Requiring Urinary Uric Acid Testing

24-hour urinary uric acid excretion should be determined in selected patients with the following characteristics 1, 4:

• Family history of young-onset gout
• Gout onset before age 25 years
• History of renal calculi (kidney stones)
• Patients being considered for uricosuric therapy

However, the 2020 ACR guidelines conditionally recommend AGAINST checking urinary uric acid for patients considered for or receiving uricosuric treatment, citing challenges with 24-hour urine collection and diet effects that negate utility given very low evidence levels 1

Patients Where Uric Acid Testing Has Limited Value

Asymptomatic Hyperuricemia

• Do NOT routinely test or treat asymptomatic hyperuricemia (elevated uric acid without gout symptoms), as pharmacological treatment is not recommended to prevent gouty arthritis, renal disease, or cardiovascular events 2
• Many people with hyperuricemia never develop gout—among those with levels >9 mg/dL, only 20% developed gout within 5 years 2

During Acute Gout Attacks

• Avoid relying on serum uric acid levels during acute attacks for diagnosis, as levels can be normal or low due to inflammatory effects 1, 5, 4
• Serum uric acid should preferably be measured at distance from a flare 4

Risk Factor and Comorbidity Assessment

All patients with gout should have assessment of risk factors and associated comorbidities, including features of metabolic syndrome 1:

• Obesity
• Hyperglycemia
• Hyperlipidemia
• Hypertension

Patients with chronic kidney disease require special attention 6, 7:

• As many as one-third of all CKD patients have gout history
• Renal function parameters (BUN, serum creatinine, creatinine clearance) should be monitored periodically in patients on allopurinol with decreased renal function or concurrent illnesses affecting renal function 3

Common Pitfalls to Avoid

• Never rule out gout based solely on normal serum uric acid levels, especially during an acute attack 5, 4
• Do not order serum uric acid as a screening test in asymptomatic patients without gout history 2
• Fasting is NOT required for uric acid testing—consistency in testing conditions is more important than fasting status 5
• Do not discontinue monitoring once target levels are achieved; continue every 6 months indefinitely 2, 5
• Nearly half of patients initiated on urate-lowering therapy do not undergo recommended uric acid monitoring within 6 months, representing a significant gap in guideline adherence 7