Test ID: SFC
Crystal Identification, Synovial Fluid
Useful For 
Suggests clinical disorders or settings where the test may be helpful
Providing a definitive diagnosis for joint disease
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 >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; their use may cause confusion masking the presence of synovial fluid crystals definitive for the disease.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Kjeldsberg C, Knight J: Body fluids: Laboratory examination of cerebrospinal, seminal, serous and synovial fluids. Third edition. Chicago, American Society of Clinical Pathologists, 1993 pp 272-283, 292-293
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