From the Guidelines
The most definitive diagnostic test for gout is synovial fluid analysis, which involves examining the fluid drawn from the affected joint under a microscope for urate crystals. This test is recommended by the American College of Physicians when clinical judgment indicates that diagnostic testing is necessary in patients with possible acute got [ 1 ]. The evidence review found moderate-quality evidence that several clinical prediction tools have sensitivities and specificities greater than 80% for diagnosing early-onoid gout compared with the reference standard of synovial fluid MSU crystal analysis [ 1 ].
Key Points to Consider
- Synovial fluid analysis has been the reference standard for gout diagnosis [ 1 ].
- Misdiagnosis or delayed diagnosis of acute gout may result in unnecessary surgery, hospitalization, delays in adequate treatment, and unnecessary prescribing of long-term treatment [ 1 ].
- Joint aspiration and synovial fluid analysis should be done if the joint can be aspirated without substantial patient discomfort by an experienced clinician who can minimize the risk for infection [ 1 ].
- A reliable, accurate source, including a polarizing microscope and a trained operator, is available to detect the presence of urate crystals [ 1 ].
Additional Diagnostic Considerations
- A uric acid blood test can be helpful but is not definitive, as levels may be normal during an acute attack or elevated in people without gout [ 1 ].
- X-rays or ultrasounds can detect joint damage or tophi in chronic gout [ 1 ].
- Clinical presentation, including sudden onset of severe pain, redness, and swelling, typically in the big toe joint, can support a gout diagnosis [ 1 ].
- A combination of clinical symptoms, elevated uric acid levels, and imaging findings can support a gout diagnosis when joint aspiration is not feasible [ 1 ].
From the Research
Diagnostic Tests for Gout
The diagnostic tests for gout (hyperuricemia) include:
- Joint aspiration to examine the synovial fluid with a polarized light microscopy to identify monosodium urate crystals 2
- Ultrasonography to disclose patterns suggestive of gout, such as the double-contour appearance of the cartilage and the snowstorm appearance of the synovial membrane 3
- Dual Energy Computed Tomography (DECT) if a joint aspiration is not feasible or inconclusive 2
- Clinical criteria from the American College of Rheumatology to diagnose gout 4
- Laboratory and radiological studies, such as serum uric acid levels and radiographic evidence of gouty arthropathy 5, 6
Key Diagnostic Features
Key diagnostic features of gout include:
- Presence of monosodium urate crystals in the joint fluid or tophus 5, 4, 2, 6
- Acute arthritis due to the deposition of urate crystals in joints in a state of hyperuricemia 2
- Characteristic joint pain, swelling, and tenderness, especially in the first metatarsophalangeal joint 5, 6
Diagnostic Challenges
Diagnostic challenges for gout include: