Serum urate level may predict flare risk in patients with gout
Approximately 95% of acute gout episodes requiring treatment occurred in patients who had a serum urate level of at least 6 mg/dL at baseline while 98% occurred in those with a baseline level of at least 5 mg/dL, according to a study using UK Biobank data on 1,773 episodes over a mean follow-up of 8.3 years.
A single measurement of serum urate level in patients with gout may help predict future risk for flares and gout-related hospitalization, a study found.
Researchers performed a retrospective study using data from the UK Biobank to determine whether serum urate level was associated with subsequent risk for acute gout flares and hospitalizations in patients with a history of gout. Serum urate levels were determined from blood samples obtained at baseline. The primary outcome measures were rate of recurrent acute gout, according to hospitalization, outpatient, and prescription/procedure records. Adjusted rate ratios were calculated with negative binomial regression. The results were published Feb. 6 by JAMA.
Overall, 3,613 patients who had a history of gout and a serum urate level obtained between April 28, 2007, and Sept. 29, 2010, were included in the study. Mean age was 60 years, and 86% were men. Mean serum urate level at baseline was 6.87 mg/dL. There were 1,773 new gout episodes requiring treatment over a mean follow-up of 8.3 years, 95% in patients whose serum urate level was at least 6 mg/dL at baseline and 98% in patients whose baseline level was at least 5 mg/dL.
Rates of acute gout flares per 1,000 person-years were 10.6 for patients with baseline urate levels below 6 mg/dL, 40.1 for those with levels of 6.0 to 6.9 mg/dL, 82.0 for those with levels of 7.0 to 7.9 mg/dL, 101.3 for those with levels of 8.0 to 8.9 mg/dL, 125.3 for those with urate levels of 9.0 to 9.9 mg/dL, and 132.8 for those with levels of 10 mg/dL or higher. Compared to the group below 6 mg/dL, respective rate ratios for flares within 10 years were 3.37, 6.93, 8.67, 10.81, and 11.42. Rates of hospitalization per 1,000 person-years during follow-up were 0.18, 0.97, 1.8, 2.2, 6.7, and 9.7, respectively, with corresponding rate ratios of 1.0, 4.70, 8.94, 10.37, 33.92, and 45.29, adjusting for age, sex, and race.
The authors noted that 55% of the UK Biobank participants could not be included in the study because they did not have primary care data available and that acute gout flares not treated by clinicians could not be measured, among other limitations. "In this retrospective study of patients with history of gout, serum urate levels at baseline were associated with the risk of subsequent gout flares and with rates of hospitalization for recurrent gout," they concluded. "These findings support using a baseline serum urate to assess risk of recurrent gout over nearly 10 years of follow-up."
An accompanying editorial noted that evidence on secondary prevention of gout is needed because guidelines, including 2016 clinical practice guidelines from ACP, have disagreed about whether to support a "treat-to-target" approach to serum urate level. The current study provides "valuable epidemiological evidence to support future prospective gout clinical trials testing the value of serum urate as a clinical predictor and as a biomarker amenable to clinical intervention to guide secondary prevention," the editorialist wrote. "These future studies should be designed for testing serum urate thresholds as treatment goals as well as their effect on meaningful clinical outcomes for patients with gout." Future trials should also enroll diverse populations and standardize serum urate analysis, among other factors, the editorialist stated. "Maybe then pervasive biases will be avoided and the question of whether serum urate is a reliable biomarker and clinically relevant risk factor amenable to intervention in gout will be resolved," he wrote.