What laboratory and imaging tests are primarily used to diagnose gout? (blood uric acid levels, synovial fluid analysis for urate crystals, imaging studies)
Hello, regarding the diagnosis of gout, doctors generally consider several tests comprehensively. I'll explain them to you in the typical order of examination:
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Blood Uric Acid Test: This is the most basic and common step. The doctor will order a blood test to check if your blood uric acid level is elevated. If the level is high, the likelihood of having gout is significant. However, it's important to note that in a small number of people, blood uric acid levels can be normal during an acute gout attack, so relying solely on this indicator cannot provide a 100% conclusive diagnosis.
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Synovial Fluid Analysis: This is the "gold standard" for diagnosing gout, meaning it's the most accurate method. If one of your joints (e.g., big toe, ankle) is severely red, swollen, hot, and painful, the doctor might use a fine needle to draw a small amount of synovial fluid from the swollen joint. Then, these fluid samples are examined under a microscope. If needle-shaped urate crystals are directly observed, then gout can be definitively diagnosed. This is like catching the "culprit" directly at the "crime scene," with irrefutable evidence.
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Imaging Studies: Mainly involves taking images to get a "transparent view" of the joints.
- Ultrasound: This examination is increasingly used; it's very convenient and involves no radiation. Ultrasound can clearly show whether urate crystals are deposited on the cartilage surface within the joint, forming a characteristic "double contour sign," which is very helpful for diagnosis.
- X-ray: If gout has recurred for many years, X-rays might show signs of bone erosion, appearing like "punched-out" lesions on the bone, known as "punched-out erosions." However, X-rays are usually normal in early gout patients.
- Dual-energy CT (DECT): This is a more advanced examination that can very intuitively highlight urate crystals in the body with different colors, making them clearly visible. It is particularly valuable for diagnosing complex cases.
In summary, doctors will consider your symptom description (e.g., whether you suddenly wake up in pain in the middle of the night, which joint is painful), combined with blood uric acid levels. If the diagnosis is still uncertain, they might recommend synovial fluid aspiration or ultrasound for further clarification.