Treatment of chronic gout. Can we determine when urate stores are depletedenough to prevent attacks of gout?

Objective. To determine if lowering of serum uric acid (SUA) concentrations below 6 mg/dl or longer duration of lowered SUA will result in depletion o f urate crystals from the knee joints and prevent further attacks of gout. Methods, A prospective study was initiated 10 years ago at Philadelphia VA Medical Center to attempt to maintain SUA levels of patients with crystal p roven gout at < 6.0 mg/dl, We recalled all 57 patients who were available d uring 1999. Patients were divided into 2 groups: Group A, with SUA still > 6 mg/dl, and Group B, with SUA less than or equal to6 mg/dl. A knee joint a spirate was requested from all asymptomatic Group B patients and many in Gr oup A. Aspirates were examined by polarized light microscopy for identifica tion of crystals. Results. There were no differences between the groups in age, sex, duration of gout, or serum creatinine. Group A (n = 38) had a mean of 6 attacks of gout for the recent year, those with tophi having the most frequent attacks . Among the 16 patients in this group who agreed to knee aspiration, monoso dium urate (MSU) crystals were found in 14, although they were asymptomatic at the time. Nineteen patients (Group B) were able to maintain serum urate levels less than or equal to 6 mg/dl for > 12 months. Nearly half of them had no attack of gout for 2 or more years, with a mean of 1 attack in the l ast year for the whole group. Three patients in whom tophi were found did n ot have major flares of gout within the past year. Knee joint aspiration wa s done on 16 asymptomatic patients. Seven (44%) still had MSU crystals pres ent in their knees. Patients in this group who were taking prophylactic col chicine did not differ with respect to the character of synovial fluid from those who had discontinued it for up to several years, although the freque ncy of attacks was less in those who continued colchicine. Conclusion, A majority of patients were able to deplete urate crystal store s in their knee joint fluids when their SUA levels were kept to less than o r equal to6 mg/dl for several years. The mechanisms for persistence in some patients, and whether such crystals have clinical implications, are not kn own. Patients with chronic gout need serum urate concentrations to be kept low to prevent further attacks.