Musculoskeletal Ultrasound in Monitoring the Efficacy of Gout: A Prospective Study Based on Tophus and Double Contour Sign

BACKGROUND: In patients with gout receiving uric acid-lowering therapy, musculoskeletal ultrasound has the potential to observe changes in gout lesions. AIMS: To analyze the effectiveness of uric acid-lowering therapy in patients with gout over one year using musculoskeletal ultrasound as a monitoring technique. STUDY DESIGN: Prospective cohort study. METHODS: A total of 215 patients meeting the 1977 American College of Rheumatology gout classification criteria and treated with uric acid-lowering therapy were separated into two groups, treat-to-target and treat-to-non-target depending on the target serum urate levels. Lower extremity joints were evaluated by ultrasound before therapy (M(0)), as well as three (M(3)), six (M(6)), and twelve (M(12)) months after therapy. At various moments during uric acid-lowering therapy, the tophus size and the semiquantitative ultrasound scoring system of double contour sign were measured in the treat-to-target and treat-to-non-target groups. RESULTS: Ninety-five tophi (45 in treat-to-target and 50 in treat-to-non-target) and sixty-seven double contour sign (34 in treat-to-target and 33 in treat-to-non-target) were evaluated longitudinally. In both groups, the long diameter, short diameter, and area of tophus in treat-to-target decreased as the duration of uric acid-lowering treatment increased. Differences in the long diameter of tophus between M(12) and M(0), M(3) and M(6) were statistically significant (P < 0.05), while differences between the other time points were not significant (P > 0.05). No statistically significant differences were observed in the short diameter and the area of tophus between M(0) and M(3) (P > 0.05), while there were statistically significant differences between other periods (P < 0.05). In treat-to-non-target, the long diameter, short diameter, and area of tophus showed a slight increase at different uric acid-lowering therapy time points. The differences in the long diameter, short diameter, and area of tophus at different uric acid-lowering therapy time points were not significant (P > 0.05). The semiquantitative ultrasound scoring system of double contour sign of treat-to-target and treat-to-non-target showed a decreasing trend with increasing uric acid-lowering therapy time, with a more pronounced drop in treat-to-target than treat-tonon- target. In treat-to-target, the difference in the semiquantitative ultrasound scoring system of double contour sign at each uric acid-lowering therapy time point was significant (P < 0.05). In treat-to-non-target, the difference in semiquantitative ultrasound scoring system of double contour sign scores between M(0) and M(3) was not statistically significant (P >0.05), but it was statistically significant for the remaining time points (P < 0.05). CONCLUSION: After one year of uric acid-lowering therapy in patients with gout, an ultrasound indicated that the size of tophus and the semiquantitative ultrasound scoring system of double contour sign score decreased dramatically in the treat-to-target group. Semiquantitative ultrasound scoring system of double contour sign score was dramatically reduced in the treat-to-non-target group, but the size of the tophus remained the same. Therefore, musculoskeletal ultrasound is an effective tool to monitor the efficacy of uric acid-lowering therapy.