A synovial fluid specimen is too viscous and difficult to aspirate. What must be done?

A synovial fluid specimen is too viscous and difficult to aspirate. What must be done?

• A. Perform test immediately
• B. Add acetic acid
• C. Add hyaluronidase
• D. Dilute specimen

Answer: (C)

Viscosity in synovial fluid is mainly due to high-molecular-weight hyaluronic acid. When the fluid is too thick, it resists aspiration and can yield an unrepresentative sample for analysis. Using hyaluronidase, an enzyme that digests hyaluronic acid, lowers the viscosity so the fluid can be aspirated more easily and the cells and constituents can be studied accurately. Diluting the specimen could help with aspiration but would dilute cells and analytes, skewing results; testing immediately won’t address the viscosity issue; adding acetic acid does not reduce viscosity and could alter cell integrity. So, hyaluronidase is the most effective and appropriate step to take.

Viscosity in synovial fluid is mainly due to high-molecular-weight hyaluronic acid. When the fluid is too thick, it resists aspiration and can yield an unrepresentative sample for analysis. Using hyaluronidase, an enzyme that digests hyaluronic acid, lowers the viscosity so the fluid can be aspirated more easily and the cells and constituents can be studied accurately. Diluting the specimen could help with aspiration but would dilute cells and analytes, skewing results; testing immediately won’t address the viscosity issue; adding acetic acid does not reduce viscosity and could alter cell integrity. So, hyaluronidase is the most effective and appropriate step to take.