Two-year reduction of dual-energy CT urate depositions during a treat-to-target strategy in gout in the NOR-Gout longitudinal study

OBJECTIVES

There is a lack of large longitudinal studies of urate deposition measured by dual-energy computed tomography (DECT) during urate lowering therapy (ULT) in people with gout. We explored longitudinal changes in DECT urate depositions during a treat-to-target strategy with ULT in gout.

METHODS

Patients with a recent gout flare and serum-urate (sUA) >360 µmol/l attended tight-control visits during escalating ULT. The treatment target was sUA <360 µmol/l, and <300 µmol/l if presence of tophi.A DECT scanner (General Electric Discovery CT750 HD) acquired data from bilateral forefeet and ankles at baseline and after one and two years. Images were scored in known order, using the semi-quantitative Bayat method, by one experienced radiologist who was blinded to serum urate and clinical data. Four regions were scored: the first metatarsophalangeal (MTP1) joint, the other joints of the toes, the ankles and midfeet, and all tendons in the feet and ankles.

RESULTS

DECT was measured at baseline in 187 of 211 patients. The mean (S.D.) serum urate level (μmol/l) decreased from 501 (80) at baseline to 311 (48) at 12 months, and 322 (67) at 24 months.DECT scores at all locations decreased during both the first and the second year (p< 0.001 for all comparisons vs baseline), both for patients achieving and not achieving the sUA treatment target.

CONCLUSIONS

In patients with gout, urate depositions in ankles and feet as measured by DECT decreased both in the first and the second year, when patients were treated using a treat-to-target ULT strategy.

POS0139 TWO-YEAR REDUCTION OF URATE LOAD IN DUAL-ENERGY CT DURING A TREAT-TO-TARGET APPROACH IN GOUT PATIENTS: RESULTS FROM A LONGITUDINAL STUDY (NOR-GOUT)

Background:

Dual-energy computed tomography (DECT) detects urate depositions, and is included in the ACR/EULAR classification criteria for gout. There is lack of longitudinal studies in large patient populations for changes in urate deposition measured by DECT during urate lowering therapy (ULT).

Objectives:

To explore by DECT the longitudinal changes urate depositions during a treat-to-target approach in gout with ULT.

Methods:

In a prospective observational study, patients with crystal-proven gout were included if they presented after a recent gout flare and with increased serum urate levels (>360 μmol/L/>6 mg/dl). In a treat-to-target approach they received ULT with escalating drug doses with monthly follow-up during the first year until the treatment target was met with serum urate <360 μmol/L or 360 µmol/L if tophi.

A DECT scanner (General Electric Discovery CT750 HD) acquired data from bilateral forefeet and ankles at 80 KW and 140 KV, processed with a software with a 2-material decomposition algorithm which colour codes urate. Follow-up DECT was performed after one and two years.

Images were scored with a semiquantitative method (Bayat et al. 2015) by one experienced radiologist in known order and blinded to serum urate and clinical data. Each scan assessed four regions: the first metatarsophalangeal (MTP1) joint, the other joints of the toes, the ankles and midfeet, and all visible tendons in the feet and ankles. Each region was then scored according to the maximum amount of urate deposition observed on visual inspection (0=no deposits, 1=dots, 2=single deposit, 3=more than one deposit). A total DECT sum score was derived by adding all values from the four regions, with a maximum score of 12.

Results:

DECT was at baseline measured in 187 of 211 patients. 95.2% were males, mean (SD) age was 56.7 (13.7) years, disease duration 8.1 (7.9) years), and 17% had clinical tophi.

The total DECT scores and all subscores decreased from baseline to 2 years (p<0.001 for all comparisons versus baseline), table 1.

The mean (SD) serum urate level (μmol/L) decreased from 501 (80) at baseline to 311 (48) at 12 months and 322 (67) at 24 months. Reaching the treatment target <360 µmol/L after year 1 or 2 was only numerically but not statistically related to reductions in DECT scores. Patients with clinical tophi at baseline had larger reductions in total DECT scores after 1 (3.4 vs. 1.5, p<0.01) and 2 years (6.5 vs. 2.3, p<0.001) than patients without tophi.

Conclusion:

During a treat-to-target approach urate deposition visualised by DECT were clearly reduced in ankles and feet after 1 year with further reduction after 2 years.

Table 1.Baseline (n=187) Mean (SD)1 year (n=157) Mean (SD)2 years (n=166) Mean (SD)MTP1 (0-3)1.4 (2.0)1.0 (1.7)0.6 (1.3)Toes (0-3)1.0 (1.8)0.6 (1.4)0.3 (1.0)Ankle/Midfoot (0-3)1.2 (2.1)0.7 (1.60.3 (1.0)Tendons (0-3)1.0 (1.7)0.5 (1.2)0.3 (0.8)Sum score (0-12)4.6 (6.4)2.8 (4.7)1.5 (3.2)

Disclosure of Interests:

Till Uhlig Speakers bureau: Grünenthal, Novartis, Consultant of: Grünenthal, Novartis, Tron Eskild: None declared, Lars Fridtjof Karoliussen: None declared, Tore K. Kvien Consultant of: AbbVie, MSD, UCB, Hospira/Pfizer, Eli-Lilly, Roche, Hikma, Orion, Sanofi, Celltrion, Sandoz, Biogen, Amgen, Egis, Ewopharma, Mylan, Grant/research support from: BMS, AbbVie, MSD, UCB, Hospira/Pfizer, Eli-Lilly, Espen A Haavardsholm Consultant of: Pfizer, UCB, Eli Lilly, Celgene, Janssen-Cilag, AbbVie and Gilead, Nicola Dalbeth Speakers bureau: Menarini, AstraZeneca, Takeda, S. Nicolaou, Consultant of: AstraZeneca, Fonterra, Takeda, Pfizer, Cymabay, Crealta, Grant/research support from: AstraZeneca, Siemens Healthcare, Hilde Berner Hammer Consultant of: AbbVie, Lilly and Novartis

[Gout - new approaches to diagnostics and treatment]

An attack of gout is extremely painful. Recurrent attacks of arthritis in one or more joints or tendon sheaths accompanied by intense pain are typical of this commonly occurring condition. As these symptoms indicate acute inflammation due to uric acid crystal deposition, good diagnostics are essential to enable initiation of drug treatment which removes the crystals deposited in tissue.