Test Catalog

Test ID: SFC    
Crystal Identification, Synovial Fluid

Useful For Suggests clinical disorders or settings where the test may be helpful

Identifying the presence and type of crystals in synovial fluid

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Birefringent crystals are found in the synovial fluid of more than 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.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

None seen

If present, crystals are identified.

Interpretation Provides information to assist in interpretation of the test results

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

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Powdered anticoagulants such as oxalate are themselves crystalline or may cause crystals to form; their use may cause false-positive results or mask the presence of synovial fluid crystals definitive for the disease.

Clinical Reference Recommendations for in-depth reading of a clinical nature

Hussong JW, Kjeldsberg CR: Kjeldsberg's Body Fluid Analysis. First edition. ASCP Press 2015