Background: The preoperative diagnosis of periprosthetic joint infection (PJI) depends on a series of blood biomarkers. Previous studies have shown that CD64 expression on blood neutrophils and monocytes has a good diagnostic efficacy for diagnosing systemic and local infections. The purpose of the present study was to investigate the role of blood CD64 in the diagnosis of PJI.
Methods: On the basis of estimations made before the study was performed, 62 patients were recruited for joint revision surgery following the failure of primary hip or knee replacement. Venous blood was obtained within 24 hours after patient admission, and flow cytometry was performed to evaluate the CD64 expression of 3 groups of white blood cells (WBCs). CD64 expression was measured as CD64 mean fluorescence intensity (CD64MFI). The neutrophil CD64 index (nCD64 index; neutrophil CD64MFI [nCD64MFI]/lymphocyte CD64MFI [lCD64MFI]) and monocyte CD64 index (mCD64 index; monocyte CD64MFI [mCD64MFI]/lCD64MFI) were then calculated. The C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) at admission, synovial fluid indicators, leukocyte esterase test results, intraoperative histological results, and tissue or synovial fluid culture results were recorded. According to the modified Musculoskeletal Infection Society (MSIS) criteria, patients were divided into the PJI group and the non-PJI group. These blood indicators were then analyzed for the diagnosis of PJI.
Results: The PJI group included 18 patients, and the non-PJI group included 44 patients. The diagnostic value of the area under the receiver operating characteristic curve (AUC) was low for lCD64MFI, the nCD64 index, and the mCD64 index. The diagnostic value for nCD64MFI was moderate, with an AUC of 0.735 (95% confidence interval [CI], 0.595 to 0.874; p = 0.004). The diagnostic value for mCD64MFI was high, with an AUC of 0.898 (95% CI, 0.821 to 0.975; p < 0.001). The cutoff value for mCD64MFI was 28,968, with a sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 1, 0.75, 0.62, and 1, respectively. This result was confirmed by internal validation with a different antibody.
Conclusions: Flow cytometry can be used for patient screening before revision surgery, and blood mCD64MFI is a promising indicator for PJI.
Level of evidence: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.