Dual-energy computed tomography (DECT) has recently been investigated in tophaceous gout.
1) How it works: DECT scanning uses two x-ray tubes positioned perpendicularly to each other and two corresponding detectors. This allows images to be acquired at two different energy levels simultaneously, providing two datasets. These are analyzed by using a 3D material decomposition algorithm that allows characterization of uric acid (given a specific color) to be contrasted with calcium and soft tissue (other colors).
2) Test characteristics: In this 2014 article in BMJ, the sensitivity and specificity of DECT for diagnosing gout was 0.90 (95% CI 0.76 to 0.97) and 0.83 (95% CI 0.68 to 0.93), respectively.
- All false negative patients were observed among patients with acute, recent-onset gout.
- All false positive patients had advanced knee osteoarthritis.
However, in another study, differences were found for tophaceous and non-tophaceous gout: this showed moderate sensitivity in non-tophaceous and high sensitivity in tophaceous gout. DECT has lower sensitivity when restricted to individual crystal-proven gouty joints in non-tophaceous disease or individual erosive lesions in tophaceous gout.
3) Conclusions: DECT may be useful, particularly when determining whether treatment aimed at gout or another entity such as rheumatoid or psoriatic arthritis would be best, but at this point DECT has not gone "primetime" at our institution at this time.