Ultrasound vs. dual energy CT for accurate diagnosis of gout
In a clinical setting, it can be difficult to accurately and quickly confirm a diagnosis of gout. Gout rates have reportedly tripled world-wide; the prevalence of gout in women has increased, and gout in the hand and wrist is being reported more frequently now.
Gout can present suddenly, with joint pain and swelling. Often, gout is thought to be isolated to the hallux, or big toe, of the foot, but literature is showing this can present in the hand and wrist as well. Gout can present also as ‘gout attacks’ in which the patient experiences sudden onset of a burning sensation.
This article examined whether ultrasound (US) or dual energy CT (DECT) was more accurate in detecting a suspected positive case of gout. DECT has previously been proposed as the gold standard. However, access to DECT can be difficult, and US may be a feasible alternative.
In this study, 180 cases of suspected gout were included, with 136 participants being men, and 44 being women. Each case of suspected gout was given a DECT by an experienced radiographer with over 5 years of experience. The DECT radiographer was blinded to the US results.
The US examination was also conducted by an experienced radiologist; this radiographer was blinded to the results of the DECT scans.
All participants underwent both radiographic imaging methods, and a diagnosis of positive or negative as assigned for each test. Uric acid blood levels were compared amongst the participants to see if this made a difference in the detection rates of the DECT and US.
It was found that US had a lower sensitivity: in the cases that DECT indicated as positive for gout, there were only a slightly higher uric acid blood levels than in those that were identified as negative. Using US on the other hand, the uric acid levels were significantly higher for those that were identified as positive as compared with those that were negative. So US may miss some of the milder cases of gout, but DECT poses its own risk of false positives as well.
The above suggests that both US and DECT have their own limitations. However, overall, the DECT remains the gold standard for detection. As access to DECT may be limited in some clinical settings, US can still be considered as a possible support for gout diagnosis, in conjunction to standard uric acid tests.
Expert opinion by Jessica Povall
This article highlights 2 possible imaging methods to diagnose gout, which certainly has clinical benefits as those presenting with gout are often in much pain, and some cannot tolerate a synovial fluid test.
While the limitations of US are notable, it is still worth considering in situations where DECT is not possible due to access or funding. Additionally, in countries where physiotherapists can directly refer for US, this can pose a quick alternative to diagnostics for a suspected case of gout.
> From: Klauser et al., Eur Radiol 28 (2018) 4174-4181. All rights reserved to The Author(s). Click here for the online summary.