Ultrasound versus dual-energy computed tomography in patients with different stages of acute gouty arthritis: methodolog
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LETTER TO THE EDITOR
Ultrasound versus dual-energy computed tomography in patients with different stages of acute gouty arthritis: methodological issues on diagnostic value Siamak Sabour 1 Received: 12 March 2020 / Revised: 12 March 2020 / Accepted: 23 March 2020 # International League of Associations for Rheumatology (ILAR) 2020
Keywords Accuracy . Acute gouty arthritis . Dual-energy computed tomography (DECT) . Gout duration . Monosodium urate (MSU) crystals . Reliability . Ultrasound (US) . Dear Editor,
I was interested to read the paper by Cunningham AJ and colleagues published in the March 2020 issue of J Surg Res [1]. Previous studies of the diagnostic accuracy of ultrasound (US) and dual-energy computed tomography (DECT) in patients with gout have reported different results. The authors aimed to compare the diagnostic value of US and DECT in patients with different stages of acute gouty arthritis. Based on the presence of monosodium urate (MSU) crystals in the synovial fluid, patients (n = 37) were divided into three groups according to gout duration: early stage (within 1 year, n = 15), middle stage (1 to 3 years, n = 12), and late stage (more than 3 years, n = 10). All the affected joints were examined by US and DECT. They reported that in the early-stage group, the sensitivity of US was significantly higher than DECT in identifying MSU deposition (66.7% vs 26.6%, p < 0.05), while in the middle- and late-stage groups, the sensitivity of US and DECT was similar. In the early-stage group, the US results in nine joints were positive (four with double contour sign, four with snowstorm sign, and one with both double contour sign and snowstorm sign), while DECT did not show any urate crystal deposits. They concluded that US should be the first choice for acute gouty arthritis, especially in patients with early-stage disease. Although this article has provided valuable information, but there are some substantial points that considering them can help the clarity of the method and an accurate
* Siamak Sabour [email protected] 1
Department of Clinical Epidemiology, School of Public Health and Safety, Safety Promotion and Injury Prevention Research Center, Shahid Beheshti University of Medical Sciences, Chamran Highway, Velenjak, Daneshjoo Blvd., Tehran, IR 1983535511, Iran
interpretation of the study. It is crucial to know that reliability (precision, repeatability) and validity (correlation, accuracy) are two completely different methodological issues of diagnostic value [2]. Sensitivity, specificity, false positive, false negative, positive predictive value (PPV), negative predictive value (NPV), likelihood ratio positive, and negative (LR+ & LR-) are among the estimates to assess accuracy of a diagnostic test [2–5]. It should be noted that, due to the limitation of reported values for accuracy (e.g., sensitivity is generally used for public health purposes and limited in clinical practice), other validity estimates such as likelihood ratios should also be taken into account. These estimates are more appro
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