Synovial fluid S100A8, S100A9, and HNP 1-3 in the diagnosis of periprosthetic joint infection: a prospective, double-blind trial

Abstract

Background Periprosthetic joint infection (PJI) is a common and serious complication after total joint arthroplasty. Early and accurate diagnosis of PJI can improve its therapeutic effect. However, there is no single method that can independently diagnose all PJI. Finding appropriate biomarkers is essential for the diagnosis of PJI. In this study, we prospectively investigated the clinical diagnostic value of synovial fluid S100 calcium-binding protein A8 (S100A8) and S100 calcium-binding protein A9 (S100A9) in PJI, and investigated the types of α-defensins that have diagnostic value for PJI. Methods Synovial fluid samples were collected from 82 patients with suspected PJI after hip and knee arthroplasty. Patients were divided into PJI group (n = 39) and non-PJI group (n = 43) according to the Musculoskeletal Infection Society (MSIS) guideline. The matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was used to determine S100A8, S100A9, α-defensins and internal reference standards (IRS) in synovial fluid. The “peak of target protein/peak of IRS” was recorded for further analysis. The receiver operating characteristic curve (ROC) was used to analyze the diagnostic efficiency of S100A8, S100A9, α-defensins for PJI. Results We detected elevated S100A8, three S100A9 variants, as well as three types of α-defensins in the synovial fluid of PJI patients by MALDI-TOF-MS. The sensitivity, specificity and the area under ROC curve (AUC) for synovial fluid S100A8 were 97.4%, 86.0% and 0.964 (95% CI: 0.929–0.998), and were 87.2%, 88.4% and 0.902 (95% CI: 0.823–0.980), respectively, for S100A9. Synovial fluid α-defensins 1–3, also known as human neutrophil peptides 1–3 (HNP 1–3), with the sensitivity, specificity and AUC of 89.7%, 83.7% and 0.933 (95% CI: 0.884–0.982), respectively. When synovial fluid S100A8, S100A9 and HNP 1–3 are combined with synovial fluid white blood cell count (SF-WBC) and polymorphonuclear neutrophil percentage (SF-PMN), the diagnostic efficiency could be improved. Conclusion Synovial fluid S100A8, S100A9 and HNP 1–3 have satisfactory diagnostic efficiency for the diagnosis of PJI.