Clinical and Interpretive

This assay is useful for providing a definitive diagnosis for joint disease.

Birefringent crystals are found in the synovial fluid of >90% of patients with acutely inflamed joints.

Monosodium urate crystals are seen in gouty fluids and calcium pyrophosphate crystals are seen in chondrocalcinosis. The urates are usually needle-shaped, and the calcium crystals are often rhomboidal. Cholesterol crystals may also be observed.

Positive identification of crystals provides a definitive diagnosis for joint disease.

Powdered anticoagulants such as oxalate are themselves crystalline; their use may cause confusion masking the presence of synovial fluid crystals definitive for the disease.