Background/Purpose: Elevated serum urate is the most important risk factor for developing gout. However, in longitudinal cohort studies, a small proportion of people with normal urate levels develop gout and the majority of those with high urate levels do not. These observations may be due to subsequent variations in serum urate over time. It is unclear whether repeated testing of serum urate improves the ability to accurately predict development of gout. This analysis aimed to examine whether single or repeat testing of serum urate more accurately predicts incident gout over time.

Methods: Individual participant data was included from three publicly available cohorts: Atherosclerosis Risk in Communities Study (ARIC), Coronary Artery Risk Development in Young Adults Study (CARDIA), and the original cohort of the Framingham Heart Study (FHS). 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. Participants with prevalent gout prior to the second measure were excluded. Receiver operator characteristic (ROC) curves and area under the curve (AUC) statistics were computed to compare the four models.

Results: 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 of participants at baseline was 49 years. The mean follow-up from the first serum urate test was 9.3 years (range 8.9-10.1 years). Overall, there was a small increase in the mean serum urate between the first and second measures (5.42 mg/dL vs. 5.71 mg/dL, P< 0.001) which were a mean (SD) of 3.5 (0.9) years apart, but the first and second measures were highly correlated (r = 0.81, P< 0.001). 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 (95% confidence intervals: 0.78-0.84) and 0.84 (95% confidence intervals: 0.81-0.87) (Table).

Conclusion: 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.

« Back to ACR Convergence 2021

ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-repeat-serum-urate-testing-superior-to-a-single-test-to-predict-incident-gout-over-time/