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Orthopaedic Implant–Associated Infections: Pathogenesis, Clinical Presentation and Management
Published in Huiliang Cao, Silver Nanoparticles for Antibacterial Devices, 2017
Determination of leukocytes and neutrophil fraction in synovial fluid is important, since it allows the detection of culture-negative PJI according to the IDSA definition (Table 13.1). The published cutoff values show a sensitivity and specificity of nearly or even more than 90%. In hip arthroplasties, Schinsky et al. (2008) suggested >4200 WBC/μL and >80% polymorphonuclear (PMN) cells for the differential count. In knee arthroplasties, the cutoff values are lower than those in hip arthroplasties. Trampuz et al. (2004) found a value of >1700 WBC/μL and >65% PMN cells for the differential count. If the synovial fluid is examined within the first 6 weeks after surgery, the leukocyte counts are still increased by the surgical trauma and hence difficult to interpret. Proposed cutoff values are >25,000 leukocytes/μL (Bedair et al. 2011). In the future, determination of alpha-defensin, which is a cationic microbicidal peptide in neutrophils, may replace the determination of leukocyte counts in synovia (Deirmengian et al. 2015). However, a direct comparison with synovial leukocytes is still missing.
Risk factors, diagnosis and management of prosthetic joint infection after total hip arthroplasty
Published in Expert Review of Medical Devices, 2019
Syed S. Ahmed, Fahima Begum, Babar Kayani, Fares S. Haddad
Human alpha defensin-1 (AD1) is a small antimicrobial protein released by local neutrophils and macrophages. It plays an important role in host defense, as both an effector and a regulator. The laboratory-based immunoassay gives a qualitative result that is specific for synovial fluid. It was developed from studies of genomes and proteomes. However, there has been the development of a quick on table intra-operative test marketed as Synavasure by Zimmer Biomet. The advantage of this being that the result will be available in 10 min. However, the accuracy of this lateral flow test has not been independently validated.