Ultrasound Reveals Decreased Urate Deposits After Urate-Lowering Therapy in Gout

Ultrasonography can show decreases in monosodium urate deposits, which correlate with decreases in serum urate, in patients with gout after urate-lowering therapy, according to a study published in Rheumatology.

Researchers in this multicenter, 6-month, prospective study evaluated the ability of ultrasonography to determine the outcomes of urate-lowering therapy for 79 patients with gout (mean disease duration 6.3 years; mean age 61.8 years; 91% men) who had double contour sign and/or tophus at the knee and/or first metatarsophalangeal joints, and were not currently receiving urate-lowering therapy. Their baseline serum urate level before beginning urate-lowering therapy for the study was 530±97 µmol/L ( 8.9 mg/dL±1.6 mg/dL). Ultrasonography was performed at baseline, 3 months, and 6 months. Primary outcomes were change in ultrasound gout features at 6 months according to final serum urate level and correlation between changes observed on ultrasound and final serum urate levels. High serum urate was defined as >360 µmol/L  (>6 mg/dL), low serum urate was defined as 300 to 360 µmol/L (5 to 6mg/dL), and very low was defined as <300 µmol/L (<5mg/dL).

Of the 79 initial participants, 67 completed the full 6 months of the study. Ten of the 67 still had high serum urate levels at 6 months, 18 out of 67 achieved very low serum urate, and 39 achieved low serum urate. Significant decreases in ultrasound features of gout were found in patients with the lowest serum urate levels (P <.001). At 6 months, a positive correlation was seen between serum urate level and decreased tophus size (r=0.54; 95% CI, 0.34-0.70; P <.0001) and serum urate level and percentage of tophus size decrease (r=0.54; 95% CI, 0.34-0.70]). An inverse correlation was seen between serum urate levels and the proportion of disappearance of double contour sign (r=-0.59; 95% CI, -0.74 to -0.40).

Study investigators conclude that their “results suggest that [ultrasonography] is an accurate tool to follow [monosodium urate] crystal dissolution under efficient [urate-lowering therapy]. The velocity of disappearance of [ultrasonography] signs of [monosodium urate] crystal deposition is correlated with [serum urate]. In the era of treat-to-target treatment, [ultrasonography] assessment should be a tool used for follow-up.”

Some authors reported receiving fees and grants from pharmaceutical companies. See the reference for complete disclosure information.  

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Reference

Ebstein E, Forien M, Norkuviene E, et al. Ultrasound evaluation in follow-up of urate-lowering therapy in gout: the USEFUL study. Rheumatology (Oxford). 2018 Oct 4. doi: 10.1093/rheumatology/key303.