Factors to Consider When Assessing the Diagnostic Accuracy of Synovial Leukocyte Count in Periprosthetic Joint Infection.

Synovial white blood cell (WBC) count and the percentage of polymorphonuclear leucocytes (PMN%) is one of the diagnostic criteria to diagnose a periprosthetic joint infection (PJI). Although the test is widely available, the diagnostic accuracy of proposed cut-off levels are influenced by several factors, such as: the affected joint, co-morbid conditions, the causative microorganism and the gathering and processing of samples in the laboratory. In this narrative review we provide an overview on how and to what extent these factors can affect the synovial WBC count and PMN% in synovial fluid.