What laboratory tests are recommended before starting gout medication?

Laboratory Tests Before Starting Gout Medication

Before initiating urate-lowering therapy (ULT) for gout, obtain serum uric acid, serum creatinine with estimated GFR, and baseline liver function tests. 1

Essential Pre-Treatment Laboratory Tests

Serum Uric Acid Level

• Measure baseline serum uric acid to establish the starting point and guide subsequent dose titration 2
• The target for ULT is serum urate <6 mg/dL (360 μmol/L), and you cannot achieve this goal without knowing the baseline 2, 3
• For severe gout with tophi or chronic arthropathy, the target may be lowered to <5 mg/dL until resolution 2, 3

Renal Function Assessment

• Obtain serum creatinine and calculate estimated GFR before starting any ULT 1
• Renal function directly determines allopurinol dosing—patients with decreased renal function require lower starting doses 1
• In patients with severely impaired renal function (CKD stage ≥4), allopurinol should be started at 50 mg daily or even 100 mg every other day 2, 1
• The FDA label specifically warns that patients with decreased renal function should be observed closely during early stages of allopurinol administration 1

Liver Function Tests

• Obtain baseline liver function tests (AST, ALT, alkaline phosphatase) particularly if pre-existing liver disease is suspected 1
• The FDA label recommends periodic liver function tests during early therapy in patients with pre-existing liver disease 1
• Patients with liver function tests >1.25 times the upper limit of normal may require dose adjustment or alternative therapy 4

Additional Laboratory Considerations

For Specific Clinical Scenarios

• 24-hour urinary uric acid excretion is conditionally recommended against before starting uricosuric therapy—it does not change management in most cases 2
• Consider checking complete blood count at baseline, as bone marrow depression has been reported with allopurinol (though rare and usually with concomitant medications) 1

For High-Risk Populations

• HLA-B*5801 testing is conditionally recommended before starting allopurinol in patients of Southeast Asian descent (Han Chinese, Korean, Thai) and African American patients due to higher risk of allopurinol hypersensitivity syndrome 2
• Testing is conditionally recommended against in other ethnic/racial groups where prevalence is low (<1%) 2

Monitoring After Initiation

Ongoing Laboratory Surveillance

• Recheck serum uric acid every 2-5 weeks during dose titration to guide escalation toward target <6 mg/dL 2, 3
• Monitor renal function periodically (BUN, serum creatinine) in patients with decreased baseline renal function or concurrent illnesses affecting kidneys (hypertension, diabetes) 1
• Reassess dosing if renal function abnormalities appear or persist 1

Common Pitfalls to Avoid

• Do not delay ULT initiation waiting for extensive laboratory workup beyond the essential tests listed above 2, 3
• Do not start allopurinol at standard 300 mg daily dose without first checking renal function—this is a major cause of adverse events 2, 1
• Do not forget to prescribe prophylactic anti-inflammatory therapy (colchicine, NSAIDs, or corticosteroids) when starting ULT, regardless of laboratory values 3, 1
• Do not check urinary uric acid levels routinely—this test rarely changes management and is conditionally recommended against 2