SAN FRANCISCO — Dual-energy computed tomography scans showed red-colored uric acid deposits in 20 consecutive patients with clinically obvious tophaceous gout but not in 10 controls with other nongout joint conditions.
The 100% sensitivity and specificity of dual-energy computed tomography (DECT) to identify uric acid deposits could provide a needed imaging tool to aid in gout diagnosis and treatment, Dr. Abdullatif M. Alarfaj said at the annual meeting of the American College of Rheumatology.
DECT assesses chemical composition and provides specific color-coded displays to differentiate between uric acid (which shows red), calcium (blue), and other renal calculi, previous investigators have shown.
The current proof-of-concept study, in addition to assessing the accuracy of DECT in gout patients, also measured the uric acid burden in peripheral joints and performed a computerized quantification of tophus volume. The volume of uric acid in each anatomic area was measured by automated volume estimation software. The sum of tophus volume in the hands, wrists, elbows, feet, ankles, and knees comprised the total uric acid volume of peripheral joints.
DECT scans identified 440 areas of urate deposition, compared with 111 areas identified on clinical examination, reported Dr. Alarfaj of the University of British Columbia, Vancouver, and his associates. The investigators have no conflicts of interest related to this study.
DECT could be used to detect subclinical tophus deposits and the extent of intra- and extra-articular gout, he said, adding it could be used to measure individual tophus volume and total burden.
The relatively new technology also may be used in evaluating nodular lesions, diagnosing concurrent gout in patients with other arthropathies, and identifying urate deposits in body areas atypical for gout. An individual DECT scan can cost about one-sixth of the amount for an MRI, Dr. Alarfaj's senior investigator, Dr. Hyon Choi, said. The DECT hardware equipment is very expensive but is used for a variety of purposes, such as imaging coronary artery calcifications and renal calculi. The technology provides dramatic color displays and can be used to create impressive three-dimensional images of uric acid deposits that could aid clinicians in communicating about the disease to patients with gout, he added. The patients in the gout group had an average 12-year history of gout and nine painful joints in the previous year. Mean serum uric acid level was 492 micromol/L; mean age was 63; 75% were male; and 12 were white. Comorbidities were present in 17 patients.