From the Guidelines
The most accurate test for diagnosing acute gout is joint aspiration with synovial fluid analysis to identify monosodium urate crystals under polarized light microscopy. This method is considered the gold standard for diagnosis, as it allows for the direct visualization of the characteristic needle-shaped, negatively birefringent crystals 1. Joint aspiration should be performed on the affected joint during an acute flare, and the presence of these crystals confirms the diagnosis.
Supplementary Tests
Supplementary tests that can aid in the diagnosis of acute gout include:
- Serum uric acid levels, although these may be normal during an acute attack and do not confirm the diagnosis alone 1
- Complete blood count and inflammatory markers (ESR, CRP), which are often elevated but non-specific
- Imaging studies like X-rays, which may show joint damage in chronic gout but are less helpful in acute cases
- Ultrasound, which can detect crystal deposits and the "double contour" sign
- Dual-energy CT, which can visualize urate deposits but is less commonly used
Clinical Diagnosis
When joint aspiration is not possible, a clinical diagnosis based on symptoms (sudden onset of severe joint pain, redness, swelling, typically in the first metatarsophalangeal joint) combined with elevated serum uric acid may guide initial treatment 1. However, crystal identification remains the gold standard, as other conditions like pseudogout and septic arthritis can present similarly.
Recommendations
Based on the evidence, joint aspiration with synovial fluid analysis is the recommended test for diagnosing acute gout, due to its high accuracy and ability to confirm the presence of monosodium urate crystals 1. Supplementary tests and clinical diagnosis can be used to support the diagnosis, but crystal identification remains the most reliable method.
From the Research
Diagnosis of Acute Gout
- The diagnosis of acute gout can be made using several methods, including clinical presentation, laboratory tests, and radiologic findings 2.
- Demonstrating the presence of monosodium urate (MSU) crystals in the joint fluid or tophus is the gold standard for the diagnosis of gout 2, 3, 4.
- Clinical criteria, such as a sudden and severe onset of pain, swelling, and tenderness in a peripheral joint or bursa, can also be used to diagnose gout 3, 5.
- Laboratory tests, such as serum uric acid levels, can be helpful in supporting the diagnosis of gout, but are not definitive 6.
Tests for Acute Gout
- Arthrocentesis, or joint aspiration, can be performed to demonstrate MSU crystals in the synovial fluid and confirm the diagnosis of gout 2, 3, 4, 6.
- Synovial fluid analysis can also be used to exclude other causes of acute arthritis, such as septic arthritis 4, 5.
- Radiologic studies, such as X-rays, can be used to evaluate joint damage and detect the presence of tophi, but are not typically used to diagnose acute gout 2.