Don’t be fooled by normal serum urate in acute gout episodes

July 18, 2008

By Bruce Jancin

PARIS (EGMN) - Serum urate levels are often normal during acute gouty arthritis attacks, according to Dr. Naomi Schlesinger.

In what Dr. Schlesinger claimed is the largest population ever amassed of acute gouty arthritis patients with documented serum urate measurements - 339 patients - 29% of individuals on long-duration allopurinol had a true-normal serum urate level, defined as 6 mg/dL or less. Among patients not on the hypouricemic agent, 11% had a true-normal serum urate level while experiencing their acute episode of gout.

“This may be attributed to the persistence of tophi and a resultant increased body uric acid pool,” commented Dr. Schlesinger, chief of rheumatology at Robert Wood Johnson Medical School, Camden, N.J.

Using a less stringent definition of normal serum urate - a value of 8 mg/dL or less - 49% of allopurinol users were classified as having a normal level during their acute attack, as were 29% not on allopurinol, according to data she presented at the annual congress of the European League Against Rheumatism.

The 339 patients included in Dr. Schlesinger’s analysis were participants in one of two earlier randomized clinical trials assessing the efficacy of 1 week of etoricoxib or indomethacin therapy in acute gout. Although Dr. Schlesinger wasn’t involved in the original studies, she obtained the complete data for both and combined the two study populations because efficacy was similar for both drugs. Prior investigations included just 41 patients (J. Rheumatol. 2002;29:1950-3), and her own earlier study of 59 patients (J. Rheumatol. 1997;24:2265-6).

Laboratory measurements in the 339 patients - including serum urate as assessed by the uricase enzyme method - were obtained at baseline and on days 2, 5, and 8.

The mean serum urate at baseline was 7.6 mg/dL in patients on long-term allopurinol and 8.5 mg/dL in those who weren’t. Similarly, on day 8, following a week of nonsteroidal anti-inflammatory drug therapy, the mean serum urate was 7.4 mg/dL in those on allopurinol and 8.7 mg/dL in those who were not.

Patients with a history of more than four gouty attacks per year or with polyarticular attacks had higher serum urate during the episode studied than those without those characteristics.

In response to audience questions, Dr. Schlesinger said it has previously been shown that an acute gouty arthritis attack can be initiated by any significant change in serum urate, whether an increase or decrease. In some cases, however, serum urate falls secondary to the acute attack as a result of cytokines released during the episode.

Dr. Schlesinger disclosed that Merck and Co. provided her with access to the complete data from the two company-sponsored clinical trials as well as support in data analysis.