Test may include pathologist interpretation of results at an additional charge. By ordering this test, the clinician acknowledges that a pathologist interpretation will be performed and billed as a separate additional charge if indicated. Crystals most commonly identified in synovial fluid are negatively birefringent uric acid (gout) and positively birefringent calcium pyrophosphate (pseudogout). Occasionally cholesterol crystals are seen. Urate crystals are almost always seen intracellularly in acute gout. Calcium pyrophosphate crystals may be detected only after multiple aspirations of affected joints.