New Classification Criteria for Gout
The 1977 ARA classification criteria for the acute arthritis of primary gout include plain radiographic changes of asymmetric swelling within a joint and subcortical cysts without erosions. These changes may be observed in conditions other than gout and are a late feature of disease. Other plain radiographic features of gout such as soft-tissue opacifications with densities between soft tissue and bone, articular and periarticular bone erosions and osteophytes at the margins of opacifications or erosions have low sensitivity (31%) but high specificity (93%) for a clinical diagnosis of gout.
No published classification criteria include advanced imaging techniques for the detection of gout. Recent reports suggest that US and dual energy computed tomography (DECT) may allow accurate identification of some patients with gout. The double contour sign on US is defined as a hyperechoic band over anechoic cartilage and is thought to represent MSU crystals coating articular cartilage. A number of different groups have reported that the presence of the double contour sign on US has high specificity for gout (95–100%) with variable sensitivity (21–92%). Only a few imaging studies have used microscopically proven disease as a gold standard. A complicating issue is that these US features can also be present in people with asymptomatic hyperuricaemia. DECT is a recently developed imaging method that allows visualization of urate deposits through detection of the chemical composition of urate. High sensitivity and specificity has been reported for crystal-proven gout by several groups. It should be noted that most advanced imaging studies have examined the classification accuracy in patients with established disease, where joint aspirate could be achieved or other clinical criteria would be satisfied. False-negative cases have been reported. The role of these techniques for gout classification in patients with early disease and any additional benefit over microscopic or clinical criteria requires careful consideration.
Imaging Considerations
The 1977 ARA classification criteria for the acute arthritis of primary gout include plain radiographic changes of asymmetric swelling within a joint and subcortical cysts without erosions. These changes may be observed in conditions other than gout and are a late feature of disease. Other plain radiographic features of gout such as soft-tissue opacifications with densities between soft tissue and bone, articular and periarticular bone erosions and osteophytes at the margins of opacifications or erosions have low sensitivity (31%) but high specificity (93%) for a clinical diagnosis of gout.
No published classification criteria include advanced imaging techniques for the detection of gout. Recent reports suggest that US and dual energy computed tomography (DECT) may allow accurate identification of some patients with gout. The double contour sign on US is defined as a hyperechoic band over anechoic cartilage and is thought to represent MSU crystals coating articular cartilage. A number of different groups have reported that the presence of the double contour sign on US has high specificity for gout (95–100%) with variable sensitivity (21–92%). Only a few imaging studies have used microscopically proven disease as a gold standard. A complicating issue is that these US features can also be present in people with asymptomatic hyperuricaemia. DECT is a recently developed imaging method that allows visualization of urate deposits through detection of the chemical composition of urate. High sensitivity and specificity has been reported for crystal-proven gout by several groups. It should be noted that most advanced imaging studies have examined the classification accuracy in patients with established disease, where joint aspirate could be achieved or other clinical criteria would be satisfied. False-negative cases have been reported. The role of these techniques for gout classification in patients with early disease and any additional benefit over microscopic or clinical criteria requires careful consideration.
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