Serum urate level is an unreliable indicator of acute gout

A normal serum urate (SU) level at presentation does not exclude an acute gouty attack. A normal level should be considered below 6.8 mg/dL rather than 8 mg/dL as is accepted and reported by several laboratories.

Schlesinger and colleagues examined serum urate levels in 339 patients enrolled in the etoricoxib trials, the largest studies of acute gout. Some participants were taking allopurinol before being randomized to etoricoxib or indomethacin to control their acute attack.

The mean baseline and day 8 SU levels were 7.1 mg/dL and 7.3 mg/dL in persons who were taking allopurinol versus 8.5 mg/dL and 8.8 mg/dL in those who were not, respectively. Overall, 14% of patients had a true normal SU level (6 mg/dL or lower) and 32% had a laboratory-defined normal SU level (8 mg/dL or lower) during an acute gouty attack. Among those taking allopurinol, 29% had a baseline true normal SU level of 6 mg/dL or lower and 49% had a baseline SU level of 8 mg/dL or lower during their acute episode.

The authors noted that more studies are needed to better understand the correlation between SU and the body uric acid pool and the relationship to timing of changes during acute gout.