Multiple serum urate testing not superior to single test for gout prediction over time: Study

New Zealand: A longitudinal study by Sarah Stewart and the team revealed that there is no added significance of repeated serum urate testing compared to a single measurement to predict incidents of gout over time. The results of the study could help in clinical practice when providing advice to individuals about their risk of developing gout.

The study findings were presented at the American College of Rheumatology (ACR) Convergence 2021, held virtually from November 3 to 10, 2021.

Uric acid is a beneficiary diagnostic tool for screening most purine metabolic disorders. Clinicians and researchers consider serum uric acid concentration as a very important diagnostic and prognostic factor of many multifactorial disorders. While elevated serum urate is a key risk factor for incidents of gout, most patients with high serum urate levels will not develop inflammatory arthritis. Furthermore, some patients with normal urate levels do develop gout.

Against the above background, Sarah Stewart, University of Auckland, Auckland, New Zealand, and the team aimed to examine whether single or repeated testing of serum urate more accurately predicts incident gout over time.

The study was a longitudinal cohort study Individual participant data were included from three publicly available cohorts. Data from paired serum urate measures 3-5 years apart, followed by an assessment of gout incidence 5-6 years from the second urate measure were used to calculate the predictive ability of four models of serum urate measurement on incident gout: the first measure, the second measure, the average of the two measures, and the highest of the two measures. Receiver operator characteristic (ROC) curves and area under the curve (AUC) statistics were computed to compare the four models.

A total of 16,017 participants were included across the three cohorts. Overall, 56% of participants were female, and 80% were European. The mean age was 49 years. The mean follow-up from the first serum urate test was 9.3 years.

The results of the study were

• There was a small increase in the mean serum urate between the first and second (5.42 mg/dL vs. 5.71 mg/dL) were a mean of 3.5 years apart, but the first and second measures were highly correlated (r = 0.81).

• No differences were observed in the predictive ability of incident gout between the four measures of serum urate measurement with ROC curve AUC statistics ranging between 0.81 to 0.84

Stewart and the team concluded that "Repeat serum urate testing is not superior to a single measure of serum urate for prediction of incident gout over approximately one decade. These results may inform the design of longitudinal studies of incident gout, and clinical practice when providing advice to individuals about their risk of developing gout."

Reference: Stewart S, Phipps-Green A, Gamble G, Stamp L, Taylor W, Neogi T, Merriman T, Dalbeth N. Is Repeat Serum Urate Testing Superior to a Single Test to Predict Incident Gout over Time? [abstract]. Arthritis Rheumatol. 2021; 73 (suppl 10). https://acrabstracts.org/abstract/is-repeat-serum-urate-testing-superior-to-a-single-test-to-predict-incident-gout-over-time/. Accessed November 25, 2021.