Introduction
The 2018 updated European League Against Rheumatism (EULAR) recommendations for the diagnosis of gout differ somewhat, but not much, from the previous EULAR gout diagnosis recommendations published in 2006. Some new recommendations have been incorporated, some have been modified, and some have been removed. These changes are summarized in Table 1. These recommendations are based on different recent studies, but in particular we must acknowledge the contribution of the results from the SUGAR study which was used to generate the EULAR/ACR 2015 gout classification criteria.
What's new: Additions to the updated EULAR recommendations for diagnosis of gout
New staging of gout
A key difference from previous recommendations is the classification of clinical and imaging findings, and how this should be weighted when compared with the gold standard of monosodium urate (MSU) crystals in synovial fluid or tophus aspirates. This overlap of clinical and imaging findings has prompted the formulation of a new staging of gout known as “subclinical gout” (or urate crystal deposition without gout symptoms).
Imaging
The 2018 EULAR recommendations stress the usefulness of imaging, including ultrasound and dual energy computed tomography specifically, for diagnosing gout, as these techniques may yield the most specific findings. They also recommend computed tomography and magnetic resonance imaging as useful tools for differential diagnosis from other inflammatory joint diseases, although this is less specific for diagnosing gout.
The new recommendations indicate that ultrasound is, to date, the preferable imaging tool for the diagnosis of gout; further discussing that it is sensitive, specific, widely available, relatively inexpensive, and non-radiating. In addition, ultrasound can be useful for diagnostic puncture and aspiration, and can be used to evaluate local inflammation through the Doppler signal.
What's changed: Previous recommendations that have been amended in the 2018 EULAR recommendations
Microscopy
The revised wording now stresses the use of gold-standard microscopy diagnosis for every patient, instead of just commenting that it permits definite diagnosis.
Clinical presentation
The new EULAR recommendations include a conceptual change from the previous recommendations, reinforcing that gout can be the cause of any kind of acute arthritis, rather than suggesting that typical clinical presentations are highly suggestive of gout. In addition, they outline specific clinical features suggestive of typical gout flares.
Risk for cardiovascular events
In addition to assessing cardiovascular risk factors as discussed in the 2006 recommendations, the updated guidelines also suggest taking a history of specific renal and cardiac events. My personal approach is to obtain specific data on major cardiovascular events, as a history of previous stroke or unstable angina is not specifically addressed in the updated recommendations.
What's gone: Recommendations no longer included in the 2018 EULAR recommendations
Although the updated paper comments that all items of the 2006 recommendations have been amended, three of these have not specifically been addressed in the 2018 recommendations.
Asymptomatic joints
The 2006 EULAR recommendations referred to the presence of MSU crystals in asymptomatic joints previously clinically affected by gout. This seems to be incorporated in the introduction, and in the section on ultrasound-guided diagnostic aspiration.
Coexistence of infectious arthritis and gout
The previous recommendations suggested a systematic implementation of synovial fluid culture, even in the presence of MSU crystals, where septic arthritis is suspected. It may seem obvious that such a clinical procedure is mandatory for good clinical practice, and so this recommendation could be discarded as unnecessary. However, my personal point of view is that, although not necessarily included as a recommendation, this could have been further discussed in the updated recommendations, specifically for acute arthritis with high acute phase reactants, systemic symptoms, or risk factors for infection being present.
Renal excretion rate of uric acid
The 2006 recommendations advised the investigation of renal excretion rate of uric acid, in order to evaluate the pathophysiologic mechanism leading to hyperuricemia. As most patients are nowadays considered to show either renal or intestinal inefficient excretion of uric acid, this recommendation is no longer useful. Nevertheless, the absence of renal underexcretion of urate (namely renal overload due to inefficient intestinal excretion) may be associated with increased risk for adverse events if uricosuric medications are to be prescribed. This is not a common clinical situation, but a short comment on the topic may have been helpful for prescribing clinicians.
Conclusion
The 2018 EULAR updated recommendations for the diagnosis of gout are centered mostly on clinical presentation, imaging tools, and evaluation of comorbidities. They discard recommendations for renal excretion rate and septic arthritis, and reformulate and keep recommendations for a gold-standard diagnosis based on microscopic synovial fluid analysis which is mandatory for any acute arthritis. An interaction between clinical features and imaging findings has allowed formulation of a new staging of gout.
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