Time-course of tophus resolution on Dual-energy CT and ultrasound after 24 months of a treat-to-target strategy: Results from GOUT-DECTUS study

Abstract

Objectives

The main objective of the study was to evaluate the kinetics of tophus volume measured with dual-energy CT (DECT) and ultrasound (US) in patients with gout during their first 24 months of treat-to-target (T2T) urate-lowering therapy.

Methods

This was a prospective, multicenter, 24-month longitudinal pilot study including ULT-naïve patients with gout and US tophi. Clinical visits, and DECT and US scans of the knees and feet were performed at baseline, 6, 12 and 24 months. The largest tophus identified by US was chosen as the index tophus. The primary outcome was the change in the absolute volume and relative change from baseline of the tophus index volume measured with US and with DECT at all timepoints, with their correlation assessed by the Spearman correlation coefficient (ρ).

Results

A total of 55 patients (63.1 (12.3) years old, predominantly male (47/55 [85.5%]), with baseline serum urate levels of 8.73 mg/dL [7.93; 9.52] were included. Index tophus volume measured with US changed from median [inter-quartile range] 0.61 cm³ [0.30; 1.20] at baseline to 0.07 cm³ [0; 0.50] at month 24, and with DECT from 0.1 cm³ [0; 0.63] at baseline to 0 cm³ [0; 0] at month 24. Relative changes in index tophus volume measured with US and DECT were respectively −56% [−90; 0] and −96% [−100; −34] at M6, −84% [−100; −13] and −100% [−100; −89] at M12, and −96% [−100; −72] and −100% [−100; −100] at M24. The correlation for relative tophus volume change was weak at month 6 (ρ = 0.39 [0.01; 0.74]) and moderate at months 12 (ρ = 0.43 [−0.14; 0.82]) and 24 (ρ = 0.42 [−0.01; 0.73]).

Conclusion

Complete tophus resolution is obtained at 24 months of T2T in DECT but not in US, which provided a greater variability of volumetric assessments throughout follow-up.