Ultrasound-detected crystal depositions and clinical flares dissolve during successful urate-lowering therapy: 5-year follow-up results from the treat-to-target NOR-Gout study.

Abstract

The aims of this 5-year study were to explore the maintenance of low serum uric acid (sUA) during treat-to-target urate-lowering therapy (T2T-ULT) and whether long-term low sUA results in continuous decrease of ultrasound-detected crystal depositions, complete dissolution of depositions, and reduction of flares. Patients with a recent gout flare were included, initiated T2T-ULT, and were followed for 5 years (outpatient clinic year 1, general practitioner years 2-5) with visits at baseline, 1, 2, and 5 years. Each visit included assessment of sUA, ultrasound examination for crystal depositions (double contour, tophi, and aggregates) in bilateral hands, elbows, knees, ankles, feet, and number of flares the previous year. Calculations included independent or paired samples t-tests, analysis of variance (ANOVA), and linear regression analyses. Of the 209 patients included at baseline (mean age 56.4 years, disease duration 7.9 years), 163 patients were examined at 5 years. At the 5-year visit, sUA was reduced from 500 (baseline) to 337 μmol/L (P < .001), 71.2% had sUA <360 μmol/L, all ultrasound depositions were reduced (P < .001), full dissolution of double contour (83.4%) and tophi (63.2%) (where examining only first metatarsophalangeal joints identified most of these patients), and only 16% had flares the previous year all of whom had higher sUA and depositions (P = .035-.006). Five years of T2T-ULT resulted in most patients achieving sUA target, reduction of crystal depositions, and dissolution of double contour and tophi in most patients. Only a few patients experienced flares, and they had higher levels of sUA and crystal depositions, supporting the importance of keeping sUA low.