Timing of Diagnostics
The timing in diagnosing prosthetic device infection is usually straightforward in that most occur due to the implantation process itself. Otherwise, infection distant from the time of implant can be caused by exposure to infectious agents in the environment, as in refillable pumps or due to changes in the immediate implant environment that encourages opportunistic infections, such as in prosthetic heart valve endocarditis.
Initial Diagnostic Approach
The diagnostic approach is directly related to the prosthetic suspected. Diagnostics include investigating the type and source of the infectious agent which will drive treatment, as well as testing for device function that may drive the decision to remove or replace it.
- A focused physical exam: Centering on the device can assess function as well as symptoms associated with malfunction or device-related infection
- Blood Tests: general testing includes a complete blood count to assess the leukocytosis (white blood cell count) to determine the general severity of infection. More specifically, blood cultures are done to identify or rule out bacteremia and the risk of sepsis.
- Aspiration of fluid for culture from suspected sites of infection: Such as joints, tissue spaces around the implanted device, or obvious pockets of exudate or transudate
- Cerebrospinal fluid: Via lumbar puncture can determine the markers for intrathecal infection (altered protein and glucose) as well as retrieve samples for culture
- Diagnostic imaging: echocardiography (in the case of heart valves), ultrasound (arteriovenous grafts, breast implants, etc.), and CT/MRI to evaluate in-situ placement and function
Later Diagnostic Testing
The success of the device relies on eradication of infection, so treatment testing using the above modalities is crucial to document a “test of cure.”