What laboratory tests and treatments are recommended for managing gout?

Laboratory Tests and Treatments for Managing Gout

Serum urate measurement is essential for diagnosis and monitoring of gout, with a target level of <6 mg/dL (<360 μmol/L) for most patients and <5 mg/dL (<300 μmol/L) for those with severe gout. 1

Diagnostic Laboratory Tests

• Identification of monosodium urate (MSU) crystals in joint fluid or tophus aspirate is the gold standard for definitive diagnosis of gout 1
• Serum uric acid level should be measured, though hyperuricemia alone is insufficient for diagnosis 1
• Renal function tests (creatinine, estimated GFR) should be performed in all patients with gout or hyperuricemia 1
• Assessment of cardiovascular risk factors is recommended in all gout patients 1
• Screening for uric acid overproduction (via 24-hour urine uric acid) should be considered in patients with:
  • Gout onset before age 25 1
  • History of urolithiasis 1

Monitoring Tests

• Regular serum urate monitoring is essential to guide urate-lowering therapy (ULT) 1
• Monitoring should include:
  • Serum urate levels 1
  • Frequency of gout attacks 1
  • Size of tophi (if present) 1
  • Renal function tests, especially when using allopurinol 1, 2
  • Liver function tests in patients with pre-existing liver disease 2

Treatment Approach

Acute Gout Attack Treatment

• First-line options (based on comorbidities and contraindications):
  • Low-dose colchicine (up to 2 mg daily, within 12 hours of flare onset) 1
  • NSAIDs with proton pump inhibitor if appropriate 1
  • Glucocorticoids (intra-articular, oral, or intramuscular) 1
  • IL-1 blockers for patients with frequent flares and contraindications to other therapies 1

Urate-Lowering Therapy (ULT)

• Indications for initiating ULT:

  • Frequent gout flares (≥2/year) 1
  • Presence of tophi 1
  • Radiographic damage attributable to gout 1
  • Chronic kidney disease stage ≥3 with first flare 1
  • Serum urate >9 mg/dL with first flare 1
  • History of urolithiasis with first flare 1

• First-line ULT:

  • Allopurinol should be started at a low dose (100 mg/day) and gradually increased to achieve target serum urate 1, 2
  • Dose adjustments needed for renal impairment (50-100 mg/day starting dose) 1, 2
  • Target maintenance dose typically 200-300 mg/day for mild gout and 400-600 mg/day for moderately severe tophaceous gout 2

• Alternative ULT options if target not achieved with allopurinol:

  • Febuxostat (no dose adjustment needed in mild-moderate renal impairment) 1
  • Uricosurics (e.g., probenecid, benzbromarone) 1, 3
  • Combination therapy (xanthine oxidase inhibitor plus uricosuric) 1
  • Pegloticase for refractory gout 1

Prophylaxis During ULT Initiation

• Prophylaxis against flares should be provided when starting ULT 1
  • Colchicine (up to 1.2 mg daily) is preferred 1
  • NSAIDs or low-dose glucocorticoids if colchicine is contraindicated 1
  • Duration depends on individual patient factors, typically 6 months 1

Treatment Targets and Monitoring

• Target serum urate level is <6 mg/dL (360 μmol/L) for most patients 1
• Lower target of <5 mg/dL (300 μmol/L) for patients with severe gout (tophi, frequent attacks) 1
• Regular monitoring of serum urate levels is essential to adjust therapy 1, 4

Common Pitfalls and Caveats

• Failure to confirm diagnosis with crystal identification when possible 1
• Treating asymptomatic hyperuricemia is generally not recommended 1
• Inadequate dosing of ULT - doses should be titrated to achieve target urate level 1, 2
• Not providing prophylaxis when initiating ULT, which can lead to flares 1, 2
• Discontinuing ULT during acute flares - ULT should be continued 2
• Not accounting for drug interactions, especially with allopurinol and azathioprine/mercaptopurine 2
• Inadequate monitoring of renal function in patients on allopurinol 1, 2
• Not addressing modifiable lifestyle factors and comorbidities 1