Diagnostic Utility of a Rapid Myeloperoxidase Test in Synovial Fluid for Chronic Periprosthetic Joint Infection

BACKGROUND: Numerous biomarkers have been identified for the diagnosis of periprosthetic joint infection (PJI), but no single biomarker has been proven to have definitive accuracy. Alpha-defensin is an excellent biomarker that is included as a minor criterion in the 2nd International Consensus Meeting (ICM) PJI diagnostic criteria; however, its high cost limits its accessibility at many general medical facilities. Consequently, alternative biomarkers for PJI diagnosis are under investigation. Myeloperoxidase (MPO), an enzyme with microbicidal properties through the catalysis of hypochlorous acid production, has emerged as a promising alternative. MPO has previously been reported as an effective biomarker for PJI. In the present study, we conducted a rapid MPO test as a point-of-care test (POCT) and evaluated its diagnostic utility. METHODS: Patients with a suspected infection after total joint arthroplasty were categorized into the PJI or aseptic failure groups according to the 2nd ICM PJI diagnostic criteria. MPO and alpha-defensin levels in synovial fluid that was collected during surgery were quantified using an enzyme-linked immunosorbent assay (ELISA), and their diagnostic accuracy was compared. Additionally, an MPO POCT was conducted, and its diagnostic accuracy was assessed. RESULTS: The investigation included 23 patients with PJI and 23 with aseptic failure. All were Japanese. MPO and alpha-defensin ELISAs exhibited a strong correlation, and, at the optimal cutoff, both tests demonstrated a sensitivity of 0.957 and a specificity of 0.957. The MPO POCT produced results in just 10 minutes and achieved a sensitivity of 1.00 and a specificity of 0.913. CONCLUSIONS: The MPO ELISA demonstrated high diagnostic accuracy for PJI, equivalent to that of the alpha-defensin test. Furthermore, the MPO POCT showed similarly high diagnostic accuracy. The MPO POCT is a promising and rapid tool for diagnosing PJI and could serve as an alternative to the alpha-defensin test. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.