DECT promising as a measure of urate burden in gout

Dual energy CT (DECT) imaging is moving steadily out of the research laboratory and towards clinical practice, as a new semi-quantitative scoring system has been shown to reliably assess urate deposition in the feet and ankles.

Professor Nicola Dalbeth, from the University of Auckland, and colleagues from New Zealand and Germany used proprietary software developed by an imaging company to analyse DECT scans of the feet and ankles of 182 patients with gout and 42 gout-free controls.

Scores were derived for four regions: the first metatarsophalangeal joint, the joints of the other four toes, the joints of the ankles/midfeet, and all visible tendons of the ankles/midfeet.

Urate deposition in each of the four regions was scored from 0 (no deposit) to 3 (more than one deposit) to provide a total score from 0 to 12.

“DECT allows visualisation and measurement of urate deposition but current measurement using volume assessment is time-consuming and does not easily allow for volume measurement of specific sites,” Professor Dalbeth said.

“We demonstrated that this new semi-quantitative scoring method not only allows measurement of deposits at specific sites but is feasible, reliable and has high discrimination.”

The tool fulfilled many requirements of the OMERACT filter – the international standard for defining the qualities of assessment tools used in rheumatology.

The scoring system had very high inter-reader correlation and all regions contributed usefully to the score.

It discriminated between participants with and without gout, and between tophaceous and non-tophaceous gout.

It also discriminated between responders and non-responders to pegloticase among eight patients who were taking the drug.

“DECT can visualise monosodium urate crystal deposits in patients with tophaceous gout, and at an earlier stage before tophi can be detected by clinical examination,” Professor Dalbeth said.

“Due to its non-invasive nature, and high sensitivity and specificity, DECT is an attractive tool for diagnosis and assessment, and has a potential role as an outcome measure to assess MSU crystal deposition in patients undergoing studies of urate-lowering therapy.

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