Background/Purpose: Rheumatology guidelines endorse a treat-to-target (TTT) approach targeting serum urate (SU) < 6 mg/dL among patients with gout who qualify for urate-lowering therapy (ULT). However, implementation of TTT remains suboptimal, in part due to frequent laboratory visits required to serially check SU for ULT titration. Prior studies (Kehasse et al., ACR abstract 2023, PMID: 29720236, PMID: 31072349) have investigated the role of capillary point-of-care (POC) SU measuring devices to reduce barriers associated with TTT. However, the results have been inconsistent, with intraclass correlation coefficients (ICC) ranging from 0.75 to 0.90 and Pearson correlation coefficient of 0.96. We sought to investigate the accuracy of a POC device, the BeneCheck Supreme (the same device brand used in a randomized trial of supported self-management in gout (PMID: 38294032) and approved in Europe for home testing), in measuring SU as compared to traditional venous laboratory analysis (TVA) among patients with gout.

Methods: We identified patients with gout who presented in-person to the rheumatology clinic at our academic hospital. Among patients who had a clinical indication to measure SU, we measured SU using both the capillary POC device and TVA on the same day. Written informed consent was required to participate in this Institutional Review Board-approved study. Demographic and clinical information was obtained through retrospective review of the electronic health record. We assessed the correlation between POC and TVA SU values using intraclass correlation coefficients (ICC). A Bland-Altman analysis assessed variability in the difference and limits of agreement between POC with TVA. The performance of POC SU measurements in identifying those with SU >6 mg/dL was analyzed using ROC curve analysis with area under curve (AUC), and was additionally adjusted for the presence of hypertension (HTN), chronic kidney disease (CKD) stage 3 or greater, and type 2 diabetes mellitus (T2DM).

Results: Our study included 27 patients, of whom 25 (92.6%) were male and 20 (74.1%) were White (Table 1). Most patients (70.4%) were on ULT. The POC SU measurements ranged from 3.4 to 10.1 mg/dL, with a mean of 6.5 mg/dL. TVA measurements ranged from 3.3 to 9.6 mg/dL, with a mean of 6.4 mg/dL. The ICC between POC and TVA measurements was 0.89 (95% CI, 0.77 to 0.95) (Figure 1). In the Bland-Altman analysis, the bias, or mean difference (POC-TVA), was 0.09 mg/dL, with limits of agreement of -1.4 to 1.6 mg/dL (Figure 2). For POC detection of SU >6 mg/dL, the unadjusted AUC was 0.94. The results did not differ significantly with inclusion of ULT in the model, but improved nominally to 0.95 with inclusion of HTN, CKD, and T2DM. The sensitivity and specificity of the POC device for detecting SU >6 mg/dL was 0.93 and 1.00, respectively.

Conclusion: In this small pilot study, the POC device and TVA for SU were strongly correlated, with a mean difference of 0.09 mg/dL between the POC and TVA measurements. The POC correctly identified 93% of individuals with SU >6 mg/dL, a clinically meaningful threshold for ULT dose titration. Such POC devices may facilitate real-time implementation of the TTT approach in gout management.

Table 1. Baseline characteristics of the study population.

Figure 1. Scatterplot of POC serum urate measurement as compared to TVA measurements, showing ICC of 0.89 (95% CI, 0.77 to 0.95).

Figure 2. Bland-Altman plot comparing POC to TVA serum urate measurements. Mean difference was 0.09 mg/dL, with limits of agreement of -1.4 to 1.6 mg/dL.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/pilot-study-testing-the-accuracy-of-a-capillary-point-of-care-device-compared-to-traditional-venous-analysis-for-serum-urate-measurements-among-patients-with-gout/