Using serum urate levels to determine the period free of gouty symptoms after withdrawal of long-term urate-lowering therapy: a prospective study.

OBJECTIVE: Withdrawal of urate-lowering therapy (ULT) is associated with recurrence of acute gouty arthritis and tophi, but no data are available about factors associated with recurrence of gouty symptoms. Therefore, life-long therapy prescription is usually advised, but the prospect of life-long therapy may contribute to very low compliance rates. Our objective was to ascertain the outcome of ULT withdrawal after long-term, documented control of serum urate levels.

METHODS: We conducted a prospective, long-term, followup study of patients treated with ULT during a 5-year period. Both diagnosis and recurrence of gout were determined based on monosodium urate crystal identification in synovial fluid or material aspirated from tophi.

RESULTS: Low average serum urate levels while receiving ULT and during the followup period after ULT withdrawal were statistically associated with the longest period in which patients were free of gouty symptoms, suggesting that depletion and formation of the body's urate pool is dependent on both time and serum urate levels. Patients whose average serum urate levels were <5.05 mg/dl while receiving ULT and <8.75 mg/dl after ULT withdrawal had the longest (>4 years) time to recurrence.

CONCLUSION: Proper and long-term reduction of serum urate level is associated with long-term periods in which patients are free of gouty symptoms, probably due to the reduction of the urate pool. These results suggest that 5-year intermittent, instead of life-long, ULT could be offered to patients with good serum urate control during ULT.