Which tests are typically included in the initial workup for suspected prosthetic joint infection?

• A. CBC, CRP/ESR, joint aspiration with culture and cell count, and imaging as needed.
• B. Only imaging; no aspiration.
• C. Serology for autoimmune markers.
• D. Joint aspiration is contraindicated.

Answer: (A)

When evaluating a suspected prosthetic joint infection, you want multiple lines of evidence to confirm infection, using both systemic indicators and direct analysis of the joint fluid, with imaging to assess the prosthesis as needed. A complete initial workup includes a CBC to look for a systemic inflammatory response, and inflammatory markers like CRP and ESR to gauge the degree of inflammation. The cornerstone is joint aspiration with synovial fluid analysis—culturing the fluid to identify the organism and performing a cell count with differential to assess the inflammatory burden, which helps distinguish infection from aseptic issues and guides antibiotic choices. Imaging adds information about the prosthesis status, such as loosening or surrounding tissue involvement, and is used to evaluate certain findings or plan management. The other options fall short because imaging alone cannot confirm infection, autoimmune serology isn’t helpful for diagnosing prosthetic joint infection, and joint aspiration is not contraindicated in this context—it's a key diagnostic step when infection is suspected.