Single measurements of serum urate levels (sUA) are unreliable for hyperuricemia classification because of spontaneous variation over time, investigators of a new study concluded.
A team led by Angelo Gaffo, MD, MSPH, of the University of Alabama at Birmingham analyzed data from a crossover clinical trial of urate-lowering therapy in young adults without a gout diagnosis (the Serum Urate Reduction to Prevent Hypertension study).
Among participants initially normouricemic, 21% converted to hyperuricemia — defined as an sUA level greater than 6.8 mg/dL — during at least 1 subsequent measurement. Individuals with screening sUA levels less than 6.0 mg/dL were much less likely to have future values in the range of hyperuricemia compared with those who had screening sUA values of 6.0 to 6.8 mg/dL (7% vs 39%), Dr Gaffo and colleagues reported online in BMC Rheumatology. Among participants initially hyperuricemic, 46% were later normouricemic during at least 1 measurement.
The finding that individuals with a sUA level less than 6.0 mg/dL are less likely to demonstrate future hyperuricemic measurements “could be considered a safer threshold to rule out intermittent hyperuricemia based on a single measurement point,” the authors wrote.
The study included 85 patients with a mean age of 27.8 years. At the time of screening, 72 individuals had normal sUA levels and 13 had hyperuricemia.
“Even though our study participants were part of a clinical trial and sUA measurements were collected in a relatively short time frame (12-14 weeks), the observed variability in sUA levels could possibly be a result of subtle factors such as time of day, diet, changes in weight, renal function and undisclosed use of medications,” the authors wrote.
Shaffer A, Rahn E, Saag K, Mudano A, Gaffo A. Variation in serum urate levels in the absence of gout and urate lowering therapy. BMC Nephrol. Sep 8;5(1):32. Published online September 8, 2021. doi:10.1186/s41927-021-00202-6