Updated EULAR diagnostic recommendations for gout highlight three-step approach
The European League Against Rheumatism (EULAR) updates its recommendations for diagnosing gout, putting emphasis on three diagnostic approaches: establishing monosodium urate (MSU) crystal deposition via synovial fluid analysis, identifying suggestive and associated clinical features of gout and hyperuricaemia, or performing imaging studies for evidence of MSU crystals.
“Despite effective treatments, gout is still often misdiagnosed and its management remains suboptimal. This may explain why the premature mortality among patients with gout remains unimproved over the last decade,” wrote lead author Professor Pascal Richette from the Hopital Lariboisiere Centre Viggo Petersen in Paris and his colleagues. [Ann Rheum Dis 2019;doi:10.1136/annrheumdis-2019-215315]
“This paper provides eight key recommendations for the diagnosis of gout to all physicians, including general practitioners, on the basis of a systematic literature review (SLR) and a Delphi consensus involving both experts and patients,” they added.
The SLR included 83 references, and the analysis generated a three-step approach to diagnosis. The first step hinges on identifying MSU crystals via synovial fluid (SF) analysis (recommendation #1). But if this is not feasible, physicians should rely on suggestive and associated clinical features of gout and presence of hyperuricaemia (recommendation #2). Finally, when a clinical diagnosis of gout is uncertain and crystal identification is not possible, patients must undergo ultrasound (US) or any alternative imaging modalities to search for evidence of MSU crystal deposition (recommendations #5 and #6).
“In these updated EULAR recommendations, the identification of crystals [in SF] using polarizing microscopy remains the gold standard for the diagnosis of gout owing to its 100 percent specificity,” according to Richette and his team.
“However, the task force acknowledges that this may have some limitations in a primary care setting where most patients with gout are diagnosed and treated,” mainly because SF analysis requires both expertise and equipment that are not readily accessible for all physicians and can be challenging to perform without patient discomfort, they pointed out.
The second recommendation underscores the value of serum uric acid (SUA) levels for establishing a gout diagnosis. However, while hyperuricaemia strongly predicts its incidence, not all patients with elevated SUA levels will develop gout.
Hence, it is recommended that SF examination should be performed in all cases of undiagnosed inflammatory arthritis, as atypical presentations of gout are not rare (recommendation #3), and that hyperuricaemia should not be used solely to diagnose gout and should only be considered when there are suggestive clinical features for the diagnosis of the disease (recommendation #4).
Since the EULAR developed its first evidence-based recommendations for diagnosing gout in 2006, several studies have explored the diagnostic value of clinical algorithms and of imaging modalities such as US or dual-energy CT. This has facilitated the identification of a continuum between a preclinical state defined by asymptomatic MSU crystal deposition within joints/tendons and occurrence of the first gout flare.
So for patients with atypical clinical features and in whom crystal identification is not feasible, the use of conventional and/or advanced imaging techniques is strongly recommended to help diagnose gout.
“As in the EULAR recommendations for the treatment of gout, the task force has emphasized in its two last recommendations [#7 and #8] the need to search for risk factors for hyperuricaemia once gout is diagnosed… [and to screen] for several comorbidities, in particular obesity, chronic kidney disease, cardiovascular diseases and components of the metabolic syndrome, which frequently coexist in patients with gout,” said Richette and colleagues.