Monitoring urate levels when on gout prophylaxis

• there is a relatively small but consistent evidence base to strongly support an association between serum uric acid level and clinical outcomes in gout
  • serum uric acid level appears to be an effective surrogate marker for treatment efficacy and long-term outcomes

The British Society for Rheumatology state (1):

• urate lowering therapy (ULT) should be discussed and offered to all patients who have a diagnosis of gout. ULT should particularly be advised in patients with the following:
  • recurring attacks (>=2 attacks in 12 months);
  • tophi;
  • chronic gouty arthritis;
  • joint damage;
  • renal impairment (estimated glomerular filtration rate (eGFR) <60 ml/min);
  • a history of urolithiasis;
  • diuretic therapy use;
  • and primary gout starting at a young age
    
    
• commencement of ULT is best delayed until inflammation has settled as ULT is better discussed when the patient is not in pain
  
  
• initial aim of ULT is to reduce and maintain the sUA (serum uric acid) level at or below a target level of 300 µmol/l to prevent further urate crystal formation and to dissolve away existing crystals. The lower the sUA the greater the velocity of crystal elimination
  • after some years of successful treatment, when tophi have resolved and the patient remains free of symptoms, the dose of ULT can be adjusted to maintain the sUA at or below a less stringent target of 360 µmol/l (6 mg/dl) to avoid further crystal deposition and the possibility of adverse effects that may be associated with a very low sUA
    
    
• key messages for primary care include (1,2):
  • the importance of initiating urate-lowering therapy - usually with allopurinol - should be started at a low dose (50-100 mg daily) and the dose then increased in 100 mg increments approximately every 4 weeks until the sUA target has been achieved (maximum dose 900 mg)
    • in patients with renal impairment, smaller increments (50 mg) should be used and the maximum dose will be lower, but target urate levels should be the same
  • the importance of intensive patient education with respect to the aims of treating gout and also optimising diet and lifestyle
  • treating episodes of acute gout promptly and effectively
  • tackling co-morbidities to improve cardiovascular risk
  • reducing the unnecessary use of urate-raising drugs such as thiazides and loop diuretics

Notes:

• NICE state:
  • start ULT at least 2 to 4 weeks after a gout flare has settled. If flares are more frequent, ULT can be started during a flare
  • aim for a target serum urate level below 360 micromol/litre (6 mg/dl)
  • consider a lower target serum urate level below 300 micromol/litre (5 mg/dl) for people with gout who:
    • have tophi or chronic gouty arthritis
    • continue to have ongoing frequent flares despite having a serum urate level below 360 micromol/litre (6 mg/dl)
      
      
• American College of Rheumatology guidance states (4):
  • a treat-to-target management strategy that includes ULT dose titration and subsequent dosing guided by serial SU measurements to achieve a target SU, over a fixed-dose ULT strategy, is strongly recommended for all patients receiving ULT
  • achieving and maintaining an SU target of <6 mg/dl over the use of no target is strongly recommended for all patients receiving ULT
    
    
• when using prophylactic treatment for gout
  • serum urate levels should be checked to guide dose escalation approximately 4 weeks after each dose increase (1)

Reference:

• (1) Hui M et al. The British Society for Rheumatology Guideline for the Management of Gout, Rheumatology, Volume 56, Issue 7, July 2017, Pages 1056–1059, https://doi.org/10.1093/rheumatology/kex150
• (2) Arthritis Research UK (2013). Synovium (38)
• (3) NICE (June 2022). Gout: diagnosis and management
• (4) Fitzgerald JD et al. 2020 American College of Rheumatology Guideline for the Management of Gout. Arthritis Care Res (Hoboken). 2020 Jun;72(6):744-760. doi: 10.1002/acr.24180. Epub 2020 May 11. Erratum in: Arthritis Care Res (Hoboken). 2020 Aug;72(8):1187. Erratum in: Arthritis Care Res (Hoboken). 2021 Mar;73(3):458. PMID: 32391934