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Changes in ultrasonography features of monosodium urate (MSU) crystal deposition may predict gouty flares after cessation of gout prophylaxis, according to study results published in Joint Bone and Spine. In a 1-year prospective study of patients with gout, higher ultrasonography tophus size was found to be associated with lower risk for relapse after stopping gout prophylaxis.
Previous studies have indicated that ultrasonography may be useful in managing urate lowering therapy (ULT) in patients with gout. To assess whether changes in ultrasonography was associated with gouty flares after stopping gout prophylaxis, the researchers conducted a 1-year prospective study at 4 clinical centers in France and Lithuania.
The study had 2 phases, including a 6-month ultrasonography follow-up after initiation of ULT followed by a 6-month clinical follow-up after cessation of gout flare prophylaxis. During the first phase, patients received ultrasonography examinations at 3-month intervals. During the second phase, patients were monitored for serum urate levels and the occurrence of gout flares. The primary study outcome was the percentage of patients showing relapse of gouty arthritis after stopping gout flare prophylaxis. Area under the receiver operating curve (AUC) was used to identify a threshold decrease in tophus size to predict gout relapse.
The study cohort included 79 patients with gout (mean age at enrollment, 61.8±14 years; median disease duration, 4 years), among whom 72 (91%) were men. Of the 49 patients who completed the 1-year follow-up, 23 (47%) had a gout relapse. A decrease in tophus size of 50% or more at month 6 was more common among patients who did not have a relapse vs those who did (54% vs 26%, respectively; P =.049). The median size of tophus at month 6 was greater among patients who had a relapse compared with those who did not (10 mm [interquartile range (IQR), 6-13 mm] vs 5 mm [IQR, 2-9 mm], respectively; P =.024).
In AUC analysis, a threshold decrease of 50.8% in tophus size had the best sensitivity/specificity ratio to predict relapse (AUC, 0.649; 95% CI, 0.488-0.809). The sensitivity and specificity for relapse were 78% and 54%, respectively. In regression models, patients who had less than a 50% decrease in tophus size during ULT were more likely than those with a 50% or more decrease to experience relapse during follow-up (odds ratio [OR], 3.35; 95% CI, 0.98-11.44).
According to these data, less reduction in tophus size during ULT may predict relapse after cessation of flare prophylaxis. Probability of relapse was increased when tophus reduction was less than 50%.
Primary study limitations included the large percentage of patients who did not complete the study and the lack of data on ULT adherence. Further study is necessary to confirm these findings.
“To better understand the impact of [ultrasonography] on ULT management and the exact clinical relevance of such [ultrasonography] follow-up, a prospective randomized control trial should be performed,” the researchers concluded.
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Reference
Ebstein E, Forien M, Norkuviene E, et al. UltraSound evaluation in follow-up of urate-lowering therapy in gout phase 2 (USEFUL-2): duration of flare prophylaxis. Joint Bone Spine. Published online September 23, 2020. doi:10.1016/j.jbspin.2020.09.014
