This test is the definitive method for diagnosing gout. When joint pain is severe, this specialized test measures the level of uric acid in the synovial fluid taken directly from the affected joint. The fluid is examined under a microscope for the tell-tale, needle-like uric acid crystals. This test is essential to distinguish gout from other forms of arthritis. A fluid sample is collected by your doctor, providing the direct, physical evidence needed to confirm your diagnosis and start the right treatment.