The inclusion criteria were primary gout arthritis and were based on the gout diagnostic criteria of the 1977 American College of Rheumatology (ACR). All patients met the criteria for classifying primary gout arthritis. Patients with rheumatoid, reactive, psoriatic, spinal, or other inflammatory arthritis were excluded. Patients with gout arthritis received anti-inflammatory therapy during an acute episode and a standardized ULT in remission. All patients received a small dose of oral anti-inflammatory drugs during ULT to prevent paroxysm of gout arthritis. During treatment, SUA was measured monthly in all participants. SUA values of all participants were plotted as a continuous curve, and all gout patients were divided into treat-to-target (TTG) and treat-to-non-target (TNTG) groups. The TTG standard curve showed a decreasing trend; the lowest SUA was below 300 µmol/l. Other gout patients who did not meet the TTG criteria were included in the TNTG group (Figure 1 ).
All US investigations were performed by a doctor who had received formal musculoskeletal US training, using a Supersonic Imagine Aixplorer machine (French) with an SL15-4 linear array probe. Joints of both lower extremities (bilateral knee, ankle, tarsal, and metatarsophalangeal joints) and some tendons of both lower extremities (bilateral quadriceps tendon, pes anserinus tendon, patellar ligament, biceps femoris tendon, iliotibial band tibial attachment, and pollicis abductor tendon) were regularly checked. The MSUS examination was performed before treatment (M0), three months after treatment (M3), six months after treatment (M6), and 12 months after treatment (M12), and the DCS and tophus ultrasound images were recorded and stored for further use. DCS was scored based on the semiquantitative ultrasound scoring system (SQUS) of the Outcome Measures in Rheumatology Clinical Trials (OMERACT) in 2021 double contour sign [(DCS)-SQUS]. The DCS-SQUS was divided into four grades as follows: 0: not at all; 1: possible; 2: definite, minor; 3: definite, severe. The maximum long diameter and the short diameter of tophus were measured based on two-dimensional ultrasound images, and the maximum area of tophus was determined using Image J. The SQUS-DCS of ultrasound images was assessed separately by two musculoskeletal ultrasonographers using a blinded method, and in case of disagreement, the two physicians consulted and reached a consensus.
All US investigations were performed by a doctor who had received formal musculoskeletal US training, using a Supersonic Imagine Aixplorer machine (French) with an SL15-4 linear array probe. Joints of both lower extremities (bilateral knee, ankle, tarsal, and metatarsophalangeal joints) and some tendons of both lower extremities (bilateral quadriceps tendon, pes anserinus tendon, patellar ligament, biceps femoris tendon, iliotibial band tibial attachment, and pollicis abductor tendon) were regularly checked. The MSUS examination was performed before treatment (M0), three months after treatment (M3), six months after treatment (M6), and 12 months after treatment (M12), and the DCS and tophus ultrasound images were recorded and stored for further use. DCS was scored based on the semiquantitative ultrasound scoring system (SQUS) of the Outcome Measures in Rheumatology Clinical Trials (OMERACT) in 2021 double contour sign [(DCS)-SQUS]. The DCS-SQUS was divided into four grades as follows: 0: not at all; 1: possible; 2: definite, minor; 3: definite, severe. The maximum long diameter and the short diameter of tophus were measured based on two-dimensional ultrasound images, and the maximum area of tophus was determined using Image J. The SQUS-DCS of ultrasound images was assessed separately by two musculoskeletal ultrasonographers using a blinded method, and in case of disagreement, the two physicians consulted and reached a consensus.
