Background/Purpose: Gout is associated with joint damage, and increased cardiovascular morbidity, so to diagnose and treat gout early is important. However, joint aspiration and microscopy not always yield the diagnosis. The latest diagnostic technique to visualize monosodium uric acid (MSU) depositions is Dual Energy CT scan (DECT).¹

We purpose to assess the sensitivity and specificity of DECT for diagnosing gout in patients with unclassified arthritis.

Methods: We included 87 consecutive patients with acute mono or oligo arthritis without prior gout diagnosis who presented to the outpatient clinic of the Department of Rheumatology of Meander Medical Centre, Amersfoort, the Netherlands, ClinicalTrials.gov number NCT03038386. Seven patients dropped out, see Figure. Patients underwent aspiration of the arthritic joint for the detection of MSU crystals (see Table) and a DECT scan of hands and wrists, knees, ankles and feet. The synovial fluid result for MSU crystals was the gold standard for gout.

Results: For demographic and clinical characteristics of the patients see Table, and for study data and outcomes see Figure. The sensitivity and specificity of DECT for gout deposition in the index joint were 0.58 (95% CI 0.43-0.72) and 0.75 (95% CI 0.57-0.89), respectively, with an area under the ROC curve of 0.67 (95% CI 0.55-0.79), p<0.05. When classifying DECT as positive if deposition was observed at the index joint and/or in other locations, sensitivity was higher: 0.77 (95% CI 0.63-0.88), but specificity lower: 0.69 (95% CI 0.48-0.86).

Conclusion: These preliminary data show the diagnostic value of DECT in patients with acute unclassified mono or oligo arthritis. Probably, DECT sensitivity is underestimated by false negative MSU results due to a sampling error, because of incorrect aspiration, or extra-articular locations of the gout, e.g. around tendons.

Table. The demographic and clinical characteristics of the patients (n=80) included in the study

* according to patient