The performance of dual-energy CT in the classification criteria of gout: a prospective study in subjects with unclassified arthritis.

Objective. To establish the performance of (subsets of) the 2015 ACR/EULAR gout classification criteria in patients with unclassified arthritis, and to determine the value of dual-energy CT (DECT) herein. Reference was the MSU crystal detection result in SF at polarization microscopy. Methods. We included subjects with acute, unclassified mono or oligoarthritis, who underwent SF analysis and DECT. Performance was assessed by calculating area under the receiver operating characteristic curve of (i) the clinical criteria subset, (ii) the clinical+serum urate subset and (iii) the full set (including DECT). Results. Of the 89 subjects enrolled, 40 met the clinical+serum urate subset criteria, and 49 (55%) subjects did not. Of these 49, 30 had a negative microscopy result, of whom 15 had positive DECT; of these 15, 14 met the full set criteria only after adding the positive DECT result. For the clinical-only subset, the areas under the curves (AUCs) were 0.68 and 0.69 without and with DECT result, respectively, and for the clinical+serum urate subset without and with DECT, AUCs were 0.81 and 0.81, respectively (results not significant). Conclusion. Adding the serum urate results to the clinical subset improves the performance, but adding the DECT result does not, neither does adding the DECT results to the clinical+serum urate subset. However, DECT seems to have an additive value in gout classification, especially when microscopy of SF is negative; 14/89 of patients (16%) only met the classification criteria with the use of DECT.