65 SYNOVIAL FLUID ANALYSIS
General Discussion
Analysis of synovial fluid plays a major role in the diagnosis of joint disease. Several classification schemes have been used to help classify joint diseases. When using classification schemes, it is important to realize that considerable overlap may occur in synovial fluid findings among different groups. In addition, more than one diagnosis may be present, such as a septic joint in a patient with rheumatoid arthritis. Findings on synovial fluid analysis may be classified as normal, noninflammatory, inflammatory, infectious, crystal-associated, and hemorrhagic.
Routine examination of synovial fluid should include: (1) gross examination of color and clarity; (2) total leukocyte and differential counts; (3) Gram’s stain and bacterial culture, both aerobic and anaerobic; and (4) crystal examination with polarizing microscopy.
Additional studies may be indicated under certain circumstances and should be guided by clinical suspicion. These studies include fungal and acid-fast stains and cultures, countercurrent immunoelectrophoresis for bacterial antigens, lactate levels, complement levels, and the presence of certain enzymes such as lactate dehydrogenase.
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