Aims. The aim of this study was to evaluate the diagnostic accuracy of the synovial alpha-defensin enzyme-linked immunosorbent assay (ELISA) for the diagnosis of prosthetic joint infection (PJI) in the work-up prior to revision of total hip (THA) and knee arthroplasty (TKA). Patients and Methods. Inclusion criteria for this prospective cohort study were acute or chronic symptoms of the index joint without specific exclusion criteria. Synovial fluid aspirates of 202 patients were analyzed and semiquantitative laboratory alpha-defensin ELISA was performed. Final diagnosis of PJI was established by examination of samples obtained during revision surgery. Results. Sensitivity and specificity of the alpha-defensin ELISA for PJI were 78.2% (95% confidence interval (CI) 66.7 to 88.5) and 96.6% (95% CI 93.0 to 99.3). Positive and negative predictive values were 89.6% (95% CI 80.6 to 97.8) and 92.2% (95% CI 87.5 to 96.1). The test remained false-negative in 22% of septic revisions, most of which were due to coagulase-negative staphylococci all occurring in either late-chronic or early-postoperative PJI. Conclusion. The routine use of synovial fluid alpha-defensin laboratory ELISA in the preoperative evaluation of symptomatic THAs and TKAs is insufficient to accurately diagnose PJI. Particularly in cases involving low-virulence organisms, such as coagulase-negative staphylococci, there remains a need for tests with a higher sensitivity. Cite this article: Bone Joint J 2019;101-B:970–977

Objectives. C-reactive protein(CRP) Used as screening test for acute periprosthetic joint infection has high sensitivity and low specificity. So there are many reasons except acute infection after total knee arthroplasty to elevate CRP level but it is unclear what reasons exactly were concerned. We therefore performed this study to determine the Causes of elevated CRP level in the early-postoperative period after primary total knee arthroplasty. Methods. Between 2005 and 2013, 502 patients undergone primary total knee arthroplasty were included. We excluded patients performed total knee arthroplasty with inflammatory arthritis and revision total knee arthroplasty, We measured the serial CRP levels in the all cases and then found cases with CRP level show elevation-depression-elevation pattern(bimodal graph) or >23.5mg/dl. We analyzed causes of elevated CRP level of that. Results. 66 patients represented bimodal pattern CRP graph. Elevation caused by periprosthetic infection were 16, Deep vein thrombosis were 10, Gastrointestinal problem were 8, urogenital cause were 10, respiratory infection was 10 and Unknown causes were 11. Conclusions. We had to know that Elevated CRP level after total knee arthroplasty can be caused by various general conditions including deep vein thrombosis can be a one of the origin elevating CRP & gastrointestinal problem, urogenital problem, respiratory infection