UltraSound evaluation in follow-up of urate-lowering therapy in gout phase 2 (USEFUL-2): Duration of flare prophylaxis.

OBJECTIVES: To determine whether changes in ultrasonography (US) features of monosodium urate crystal deposition is associated with the number of gouty flares after stopping gout flare prophylaxis. METHODS: We performed a 1-year multicentre prospective study including patients with proven gout and US features of gout. The first phase of the study was a 6-month US follow-up after starting urate-lowering therapy (ULT) with gout flare prophylaxis. After 6 months of ULT, gout flare prophylaxis was stopped, followed by a clinical follow-up (M6 to 12) and ULT was maintained. Outcomes were the proportion of relapsing patients between M6 and M12 according to changes of US features of gout and determining a threshold decrease in tophus size according to the probability of relapse. RESULTS: We included 79 gouty patients [mean (±SD) age 61.8±14 years, 91% males, median disease duration 4 (IQR 1.5;10) years]. Among the 49 completers at M12, 23 (47%) experienced relapse. Decrease in tophus size ≥50% at M6 was more frequent without than with relapse (54% vs. 26%, P=0.049). On ROC curve analysis, a threshold decrease of 50.8% in tophus size had the best sensitivity/specificity ratio to predict relapse [AUC 0.649 (95% confidence interval 0.488; 0.809)]. Probability of relapse was increased for patients with a decrease in tophus size <50% between M0 and M6 [OR 3.35 (95% confidence interval 0.98; 11.44)]. CONCLUSION: A high reduction in US tophus size is associated with lower probability of relapse after stopping gout prophylaxis. US follow-up may be useful for managing ULT and gout flare prophylaxis.

Ultrasound evaluation in follow-up of urate-lowering therapy in gout: the USEFUL study.

OBJECTIVES: We aimed to determine the ability of ultrasonography (US) to show disappearance of urate deposits in gouty patients requiring urate-lowering therapy (ULT). METHODS: We performed a 6-month multicentre prospective study including patients with: proven gout; presence of US features of gout (tophus and/or double contour sign) at the knee and/or first metatarsophalangeal joints; and no current ULT. US evaluations were performed at baseline and at months 3 and 6 (M3, M6) after starting ULT. Outcomes were: the change in US features of gout at M6 according to final (M6) serum urate (SU) level (high, > 360 µmol/l, i.e. > 6 mg/dl; low, 300-360 µmol/l, i.e. 5-6 mg/dl; very low, < 300 µmol/l, i.e. < 5 mg/dl); and correlation between changed US features and final SU level. RESULTS: We included 79 gouty patients (mean ± s.d., age 61.8 (14) years, 91% males, disease duration 6.3 (6.1) years). Baseline SU level was 530 ± 97 µmol/l (i.e. 8.9 mg/dl ± 1.6mg/dl). At least one US tophus and double contour sign was observed in 74 (94%) and 68 (86%) patients, respectively. Among the 67 completers at M6, 18 and 39 achieved a very low and low SU level, respectively. We found a significant decrease in US features of gout among patients with the lowest SU level (P < 0.001). Final M6 SU level was positively correlated with decreased size of tophus (r = 0.54 [95% CI: 0.34, 0.70], P < 0.0001), and inversely correlated with proportion of double contour sign disappearance (r=-0.59 [-0.74, -0.40]). CONCLUSION: US can show decreased urate deposition after ULT, which is correlated with decreased SU level. The responsiveness of US in gout is demonstrated and can be useful for gout follow-up and adherence to ULT.

Ultrasonography in gout: a case-control study.

OBJECTIVES: To determine the sensitivity and specificity of ultrasonography for gout, and to investigate the relationship with severity of gout. METHODS: In this case-control study, we prospectively enrolled 53 patients with crystal-proven gout and 50 controls. Ultrasonography was performed on 10 joints for each patient (metatarsophalangeal [MTP] joints 1-2, knees, metacarpophalangeal [MCP] joints 2-3) to determine the prevalence of the double contour (DC) sign and tophi in each site. RESULTS: We assessed 530 joints in gouty patients and 500 in controls. Gouty patients had a mean disease duration 9.2±10.7 years and a mean of 14.7±19.8 acute attacks. Clinical exam revealed tophi in 44% of patients. Mean urate level was 656.7±145.3 µM. Inter-reader agreement between the 2 sonographers was excellent for both DC sign and tophi. The frequency of the DC sign in MTPs, knees and MCPs for gouty patients and controls was 67% vs. 2%, 57% vs. 0%, and 21% vs. 0%, respectively (all p<0.001), whereas that of tophi, only found in gouty patients, was 74%, 42% and 22%, respectively (p<0.001). The sensitivity of the DC sign was 67% for MTPs, 57% for knees and 21% for MCPs, and specificity was high (all >98%). The sensitivity of tophi was 74%, 42% and 22%, respectively, and specificity 100% for all sites. For MTPs, the DC sign, but not tophi, was significantly associated with uricemia (p<0.05) and disease duration (p=0.01). CONCLUSIONS: Ultrasonography has good sensitivity and specificity to diagnose gout. Sensitivity depends on disease duration, joint site and severity of the disease.