Equine myeloperoxidase: a novel biomarker in synovial fluid for the diagnosis of infection.
Authors: Wauters J, Pille F, Martens A, Franck T, Serteyn D, Gasthuys F, Meyer E
Journal: Equine veterinary journal
Summary
# Editorial Summary: Equine Myeloperoxidase as a Diagnostic Tool for Joint Infection Diagnosing septic arthritis in horses remains clinically challenging despite the serious consequences of delayed treatment, making the development of reliable synovial fluid biomarkers increasingly valuable. Wauters and colleagues evaluated whether myeloperoxidase (MPO)—an enzyme released by activated neutrophils—could improve discrimination between infectious and non-infectious joint disease by measuring both total and enzymatically active MPO in synovial fluid from healthy joints, those with osteochondritis dissecans, traumatic synovitis, and culture-confirmed infections using horse-specific ELISA and SIEFED techniques. Infected joints contained significantly elevated levels of both total and active MPO compared with all non-infectious conditions, with optimal cut-off values established at 5000 ng/ml and 350 ng/ml respectively, demonstrating fair sensitivity and specificity alongside positive and negative predictive values suitable for clinical decision-making. Critically, MPO levels showed no correlation with horse age or joint location, enhancing its potential as a broadly applicable diagnostic marker independent of these variables. For practitioners encountering inconclusive white blood cell counts or borderline total protein levels in synovial fluid—a common diagnostic dilemma in field cases—MPO analysis offers a rapid, specific complementary test that could meaningfully reduce diagnostic uncertainty and facilitate earlier therapeutic intervention in suspected septic joints.
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Practical Takeaways
- •Synovial fluid MPO analysis provides a rapid, objective complement to traditional diagnostics (WBC count, protein levels) when differentiating septic from non-septic joint disease
- •Two reliable detection methods (ELISA and SIEFED) are available for clinical use, allowing flexibility based on laboratory capabilities and turnaround time requirements
- •This biomarker is particularly valuable when conventional synovial fluid parameters are inconclusive, helping reduce diagnostic uncertainty in equine joint infections
Key Findings
- •Synovial fluid MPO levels were significantly higher in culture-confirmed infected joints compared to healthy joints, OCD, and traumatic synovitis groups
- •Cut-off values of 5000 ng/ml for total MPO and 350 ng/ml for active MPO demonstrated fair sensitivity, specificity, and predictive values for infection diagnosis
- •Both ELISA and SIEFED techniques successfully detected equine MPO with confirmed antibody specificity by Western blot analysis
- •MPO levels showed no correlation with horse age or specific joint affected, supporting its use as a generalizable diagnostic biomarker