What is the diagnostic workup for gout (gouty arthritis)?

From the Guidelines

The diagnostic workup for gout should include a thorough history, physical examination, laboratory tests, and sometimes imaging studies, with joint fluid aspiration and analysis being the gold standard diagnostic test, as recommended by the European League Against Rheumatism in 2020 1. The workup for gout should start by obtaining serum uric acid levels, though normal levels don't exclude gout during an acute attack.

• Joint fluid aspiration and analysis is the gold standard diagnostic test, revealing negatively birefringent monosodium urate crystals under polarized microscopy.
• Complete blood count, renal function tests, and inflammatory markers (ESR, CRP) should be ordered to assess overall health and rule out other conditions.
• Consider checking lipid profile, glucose, and liver function tests as comorbidities are common.
• X-rays may show characteristic erosions with overhanging edges in chronic gout but are often normal in early disease.
• Ultrasound can detect crystal deposits and the "double contour" sign, while dual-energy CT can specifically identify urate deposits in complex cases.
• Additional workup should address potential underlying causes of hyperuricemia, including medications review, assessment for metabolic syndrome, and screening for conditions that increase cell turnover, as suggested by the American College of Physicians in 2017 1. This comprehensive approach helps confirm the diagnosis of gout while identifying contributing factors and comorbidities that require management alongside the primary condition.
• The European League Against Rheumatism recommends searching for crystals in synovial fluid or tophus aspirates in every person with suspected gout, as it allows for a definitive diagnosis of gout 1.
• The American College of Physicians also recommends using synovial fluid analysis when clinical judgment indicates that diagnostic testing is necessary in patients with possible acute gout, although this is a weak recommendation based on low-quality evidence 1.

From the Research

Diagnostic Workup for Gout

The diagnostic workup for gout involves several steps, including:

• Clinical evaluation: A thorough patient history and physical examination are critical to a presumptive diagnosis of gout 2
• Laboratory tests:
  • Serum urate measurement at the time of an acute attack and at follow-up 2 weeks later 2
  • Xanthine and hypoxanthine levels, which have been reported to be high in gout patients with hyperuricemia and presumed to be gout biomarkers 3
• Radiologic findings: Although not always performed, radiologic studies can be helpful in making the diagnosis of gout 4
• Synovial fluid aspiration and analysis: This is the gold standard for making the diagnosis of gout, as it can demonstrate the presence of monosodium urate (MSU) crystals in the joint fluid or tophus 4, 2

Classification Criteria

The diagnosis of gout can be made using various classification criteria, including:

• American Rheumatism Association 1977 criteria, which include hyperuricemia as the only biochemical index 3
• Clinical, radiologic, and laboratory criteria, which can be helpful in making the diagnosis of gout in the absence of demonstrating the presence of MSU crystals in aspirated joint fluid or tophus 4

Limitations of Diagnostic Tests

It's worth noting that:

• Hyperuricemia is not always present in gout patients, especially during an acute attack 3
• Nearly half of the time gout occurs without hyperuricemia, which leads to an urgent need to find new substitute diagnostic criteria for gout 3