To examine the performance of ultrasound (US) for the diagnosis of gout using the presence of monosodium urate monohydrate (MSU) crystals as the gold standard.
We analyzed data from the Study for Updated Gout Classification Criteria (SUGAR), a large, multicenter observational cross-sectional study of consecutive subjects with at least 1 swollen joint who conceivably may have gout. All subjects underwent arthrocentesis; cases were subjects with confirmed MSU crystals. Rheumatologists or radiologists who were blinded with regard to the results of the MSU crystal analysis performed US on 1 or more clinically affected joints. US findings of interest were double contour sign, tophus, and snowstorm appearance. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Multivariable logistic regression models were used to examine factors associated with positive US results among subjects with gout.
US was performed in 824 subjects (416 cases and 408 controls). The sensitivity, specificity, PPV, and NPV for the presence of any 1 of the features were 76.9%, 84.3%, 83.3%, and 78.2%, respectively. Sensitivity was higher among subjects with a disease duration of ≥2 years and among subjects with subcutaneous nodules on examination (suspected tophus). Associations with a positive US finding included suspected clinical tophus (odds ratio [OR] 4.77 [95% confidence interval (95% CI) 2.23–10.21]), any abnormality on plain radiography (OR 4.68 [95% CI 2.68–8.17]), and serum urate level (OR 1.31 [95% CI 1.06–1.62]).
US features of MSU crystal deposition had high specificity and high PPV but more limited sensitivity for early gout. The specificity remained high in subjects with early disease and without clinical signs of tophi.
Liver stiffness measurement (LSM) is the most widely used non-invasive alternative to biopsy for assessing liver fibrosis in the UK. Virtual touch quantification (VTq, also known as acoustic radiation force impulse) is the principal available alternative to transient elastography (Fibroscan) and is delivered via software enhancements to standard ultrasound (US) machines. It has recently been endorsed by National Institute for Health and Care Excellence in terms of both accuracy and cost-effectiveness for use in viral hepatitis. However, while an increasing proportion of radiologists use VTq, familiarity among gastroenterologists and trainees with LSM techniques is variable and implementation is patchy. This review considers the background, evidence for and practical use of VTq elastography in clinical practice in the UK. Potential future developments in this rapidly evolving field are also highlighted.