Dual-Energy CT Accurately Diagnoses Urate Crystal Deposition in Gout; Limited Sensitivity for Short-Stage Gout

The use of dual-energy computed tomography (DECT), based on gemstone spectral imagine (GSI) technology, shows promising diagnostic accuracy for the detection of monosodium urate (MSU) crystal deposition in gout but has limited diagnostic sensitivity for short-term gout, according to study results published in Advances in Rheumatology.

In the past decade, the clinical use of DECT to diagnose gout has dramatically increased, with image acquisition obtained based on 80 or 140 kVp that operates at either the source or the detector level. The use of DECT to evaluate MSU crystals is promising as current methods are time-consuming.

A team of researchers conducted a cross-sectional study to determine the accuracy, sensitivity, and specificity of single-source DECT GSI in the detection of MSU crystal deposition at the feet and ankles of patients with suspected (≤1 year), middle (1-3 years), and late (>3 years) stages of gout; to understand the correlation between clinical data and urate deposition evaluated by single-source DECT GSI at the feet/ankles; and to assesses the effect of artifacts on diagnostic performance of single-source DECT in gout.

Patients with suspected gout of the feet/ankles were included in the study between December 2016 and 2020. The final gout diagnosis was determined by a rheumatologist, based on the 2015 European Alliance of Associations for Rheumatology/American College of Rheumatology (EULAR/ACR) classification criteria. Scans were conducted using the single-source DECT systems, the tube voltage of which were switched between 80 and 140 kVp in less than 0.05 μs.

A total of 196 patients were included in the analysis – 125 patients (mean age, 56.16 years) and 71 patients (mean age, 51.68 years) were examined with Discovery CT750HD and Revolution CT, respectively. A total of 33 patients (16.8%) had a history of tophus. The average disease duration was 7.52 years; the average uric acid level at baseline was 465.11 mmol/L; and 37 patients were receiving urate-lowering treatment during evaluation.

The sensitivity, specificity, and area under receiver operating characteristic curve (AUC) for the patients with early-stage gout were 38.10, 96.43%, and 0.673, respectively; 62.96, 100.00%, and 0.815 for patients with middle-stage gout, respectively; and 77.55, 87.50%, and 0.825 for patients with late-stage gout, respectively.

Compared with the early-stage gout cohort, the middle-stage gout cohort had higher overall diagnostic accuracies for the AUC of DECT (Discovery CT750HD and Revolution CT). Crystals of MSU were found to deposit on the first metatarsal joints and ankles and midfeet, and total urate scores were greatly affected by age, the presence of tophus, bone erosion, and disease duration. Researchers did not observe significant differences between the case and control groups in the positive detection of nail and skin artifacts, vascular calcification, or noise artifact.

“DECT GSI (Discovery CT750HD and Revolution CT) showed promising diagnostic accuracy for the detection of MSU crystal deposition in gout but had limited diagnostic sensitivity for short-stage gout,” the researchers concluded.