Fluctuations of Serum Urate Levels in Gout Patients Over 2 Years

Hyperuricaemia, elevated levels of serum urate in the blood, leads to the formation of monosodium urate (MSU) crystals. MSU deposits in and around the joints, resulting in gout. If gout is uncontrolled, patients may experience frequent flares of inflammation and pain. To treat gout and mitigate the symptoms, urate-lowering therapies (ULT) are often prescribed to patients to lower their serum urate levels, and in turn, prevent painful gout flares. Prior studies have reported that gout flares are frequent after beginning ULT, particularly 3 to 6 months after starting treatment.

Gout flares can be triggered by a variety of things such as purine-rich diets and alcohol consumption. Increases in SU have also been observed in patients postoperatively who underwent bariatric surgery. While SU fluctuations can trigger gout flares, the evidence is lacking regarding the fluctuation in SU over time during ULT.

Researchers at the Center for Treatment of Rheumatic and Musculoskeletal Diseases at Diakonhjemmet Hospital in Oslo, Norway, investigated the ways fluctuation and changes in SU during an intensive ULT approach were related to gout flares. The study, published in Clinical Rheumatology, prospectively evaluated 173 patients with increased SU and a recent flare who were being treated with ULT over 1 year, with follow-up at 2 years.

SU fluctuation was measured during each study visit, and was defined by the authors as “the absolute sum of all observed SU changes between adjacent visits accumulated from baseline to time of observation.” SU fluctuation and change were compared between patients with and without gout flares during the study period. The authors also examined the effect of larger SU changes between two consecutive visits with predefined thresholds of >30 µmol/L, >60 µmol/L, and >90 µmol/L change in SU levels.

During the first year of the study period, 80.6% of patients experienced a gout flare, and 26.0% of patients experienced a gout flare during the second year. For patients with a gout flare, the sum of SU changes was higher compared with patients without a gout flare during year 1.

“No relation to flares was seen for SU changes between adjacent visits, and not whether patients after initially reaching the treatment target again increased SU towards levels with increased risk of MSU crystal formation,” the authors said. “We found thus that the sum of absolute SU changes over an observation period was a useful indicator of fluctuation, being associated with the occurrence of flare during year one.”

The authors also note that while “Our findings require confirmation in other longitudinal studies,” they concluded that, “Findings support existing treatment recommendations with a focus on the gradual increase of ULT to lower SU and reinforce a need for treatment adherence to avoid SU fluctuation.”