Oxypurinol and urate assay
Urate concentrations were measured using a Roche COBAS 6000 chemistry
analyzer (Roche Diagnostics, Indianapolis, IN) using the enzymatic
method with a limit detection of 0.2 mg/dL. The inter-assay coefficient
of variation was 1.3% at 5.50 mg/dL and 2.0% at 9.67 mg/dL. Oxypurinol
concentrations were measured as described in previous
publication.25 None of the SU, serum oxypurinol, and
urine oxypurinol concentrations were below the limit of quantification.