Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Quantitative Documentation of Tophus Volume Change Using Dual Energy Computed Tomography Scans.

Abufayyah3,  Mohammed, Nicolaou3,  Savvas, Eftekhari3,  Arash, Reid3,  Graham, Shojania2,  Kamran, Co3,  Steven, Choi1,  Hyon K.

Boston University School of Medicine, Vancouver, BC, Canada
Univ of British Columbia, Vancouver, BC, Canada
University of British Columbia, Vancouver, BC, Canada

Objectives:

Dual Energy Computed Tomography (DECT) scans produce obvious color displays for urate deposits and allow quantitative volumetric measurement of urate deposits in the articular and extra-articular structures. This report describes our recent experience on the potential utility of DECT scans to document changes in tophus volume in patients with tophaceous gout receiving urate lowering therapy.

Methods:

This study included 12 consecutive patients with tophaceous gout who received urate-lowering therapy agents at our rheumatology clinic and underwent initial and follow-up DECT scans on at least one of the following four peripheral articular regions - elbows, wrists/hands, knees, and ankles/feet. The average interval between the two scans was 19 months (range, 11 – 29 months). Using a computer automated procedure to measure the apparent color-coded information of the urate deposits on DECT scans, we measured volumes of uric acid deposition in cm3 in initial and follow-up scans. The Wilcoxon rank-sum test was used to compare changes in tophus volume.

Results:

All 12 patients (mean age, 67 yrs) with tophaceous gout showed color-coded urate deposits. Ten patients showed clinical improvement due to urate lowering therapy, with lowering serum urate levels (mean follow-up level, 5.9mg/dl) and lower frequency of gout attacks (mean, 1.4/yr), whereas two patients showed clinical deterioration during the follow-up (mean serum uric acid levels=9.1 mg/dl and mean gout attacks 7.5/year). All ten responders showed reduction in tophus volume with a median reduction of 64% (p = 0.002) (See Table and Figure below). Total volumes from 10 patients reduced from 322.1 cm3 to 107.35 cm3 (67% reduction). Improvement of individual articular regions in these 10 patients ranged from 41% to 83% (all p-values <0.05). In contrast, the two non-responders showed 36% increase in total tophus volume (total volumes from 157.74 cm3 to 246.19 cm3) with similarly increasing volumes in individual articular regions (range, 31% to 38% increase).

Table. Changes in DECT Urate Volume after Urate-Lowering Therapies among Ten Responders*

   Regions of Urate Deposition 
NoAge/SexHands & WristsElbowsKneesFeet & AnkiesTotal Volume (Reduction %)
   Initial Scan ® Follow-Up Scan (Volume by DECT, cm3)
163/M2.70®0.120.05®033.37®29.313.48®2.6939.6®32.12 (18%)
281/M2.45®0.330.41®0.418.44®5.7212.67®1.9323.97®8.39 (65%)
364/M0.67®0.10.22®0.113.3®0.370.42®0.094.61®0.67 (86%)
472/M0.57®0.240.27®0.230®020.1®6.8720.94®7.34 (65%)
575/M38.37®6.2518.58®10.3757.66®15.2980.96®14.14195.57®46.05 (77%)
639/M1.75®0.820.37®0.316.38®4.19NA8.5®5.32 (37%)
772/M1.51®0.22NA2.44®1.346.91®3.039.35®4.37 (53%)
884/M0.02®0.010.67®0.57NANA0.69®0.58 (16%)
964/MNANA0.92®0.35NA0.92®0.35 (62%)
1056/MNANA17.95®2.16NA17.95®2.16 (88%)
Total 48.04®8.0920.57®12130.46®58.73124.54®28.75322.10®107.35 (67%)
P-values 0.0080.030.0080.030.002

Figure A. The initial 30-DECT scan image of patient #4 (see Table) showing extensive urate deposits at the first metacarpophalangeal joint. B. The follow-up scan showing reduced MSU deposits on after urate-lowering therapy (Arrows denote tophi that appear in red in color display and appear in gray in black/white display).

Conclusion:

This study provides a proof of concept for the ability of DECT scan as a potentially sensitive, quantitative imaging tool in assessing urate volume changes in patients with tophaceous gout. These data provide support for further prospective studies to examine the utility of DECT as a reliable imaging tool in following the response to urate-lowering therapy, through measurement of individual tophus volumes and total tophus burden in clinical care and trials.

To cite this abstract, please use the following information:
Abufayyah, Mohammed, Nicolaou, Savvas, Eftekhari, Arash, Reid, Graham, Shojania, Kamran, Co, Steven, et al; Quantitative Documentation of Tophus Volume Change Using Dual Energy Computed Tomography Scans. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :2152
DOI: 10.1002/art.29916

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