Development of a Dual-Energy Computed Tomography Scoring System for Measurement of Urate Deposition in Gout

Objective. To develop a semiquantitative dual-energy computed tomography (DECT) scoring system for measurement of urate deposition in gout. Methods. Following a structured review of images, a semiquantitative DECT urate scoring method for foot/ankle scans was developed for testing. This method included 4 regions, each scored 0-3, with a maximum total DECT urate score of 12. DECT scans from 224 patients (182 with gout, 42 without gout) were scored by 2 independent readers. Automated urate volumes were also measured. Paired scans from 8 patients receiving pegloticase were analyzed, and a timing exercise was undertaken. The properties of the DECT urate score were analyzed according to the Outcome Measures in Rheumatology (OMERACT) filter. Results. The interreader intraclass correlation coefficient (95% confidence interval) for the DECT urate score was 0.98 (0.97-0.98). All scored regions contributed to the total DECT urate score. DECT urate scores and volumes were highly correlated (r = 0.91, P < 0.0001). Both DECT urate scores and volumes discriminated between gout and nongout control participants and between the tophaceous gout, nontophaceous gout, and control groups. Compared with urate volume, the DECT urate score had greater ability to discriminate between responders and nonresponders to pegloticase therapy (P < 0.001 for DECT urate score and P > 0.05 for volume). The mean +/- SD time required for the DECT urate score was 121 2 seconds and for urate volume was 240 2 seconds (P = 2 x 10(-31)) Conclusion. We have developed a novel semiquantitative DECT scoring method for measurement of urate deposition in the feet/ankles. This method fulfills many aspects of the OMERACT filter.