Repeat Knee Aspiration
In the absence of reliable evidence, it is the opinion of the work group that a repeat knee aspiration be performed when there is a discrepancy between the probability of periprosthetic joint infection and the initial aspiration culture result.

Rationale
It was the consensus of the work group that data be extrapolated from recommendation 5 for periprosthetic knee infections even though there was no reliable evidence pertaining to the utility of a repeat knee aspiration. (The available study5 enrolled too few patients to be reliable.) 
 
It is the opinion of the work group that repeat aspiration be performed when 1) the clinical probability of infection is low but the initial aspiration culture result is positive, or 2) if the clinical probability of infection is high and the initial aspiration culture result is negative.
 
The final decision on whether to perform a repeat knee aspiration may also be influenced by other factors.  The results of additional tests will raise or lower the probability of periprosthetic infection. Thus, depending on the results of ESR and CRP, as well as the synovial fluid white blood cell count and differential, the diagnosis or exclusion of periprosthetic infection may be more apparent and repeat aspiration may not be necessary.