Evaluation of myeloperoxidase in synovial fluid as a biomarker for chronic periprosthetic joint infection

Purpose There is no single biomarker that can perfectly diagnose periprosthetic joint infection (PJI). As diagnosing PJI remains a major challenge, accurate and rapid development of a biomarker is required. Myeloperoxidase (MPO) is a bactericidal enzyme that acts against pathogenic microorganisms, such as those found in PJI. We aimed to determine whether elevated MPO levels could be detected in infected synovial fluid and to evaluate its utility as a biomarker for diagnosing chronic PJI. Methods Patients who underwent revision total joint arthroplasty were categorised into two groups according to the criteria of the second International Consensus Meeting on Musculoskeletal Infection: chronic PJI or aseptic failure. MPO was measured in synovial fluid collected during surgery. Receiver operating characteristic curves were drawn, and the area under the curve, 95% confidence intervals, and sensitivity/specificity were calculated. Results Synovial fluid was obtained from 37 patients. Nineteen patients were categorised into the chronic PJI group and 18 in the aseptic failure group. MPO levels in the synovial fluid were significantly higher in the chronic PJI group than in the aseptic failure group ( p < 0.001). This measurement demonstrated the diagnostic accuracy of MPO for diagnosing chronic PJI with high sensitivity and specificity. Conclusion Although the results are debatable owing to the small sample size, measurement of MPO demonstrates high accuracy as a biomarker for diagnosing chronic PJI, and it may detect culture-negative chronic PJI. Furthermore, MPO can measure host response to chronic PJI without the potential of contamination.