Synovial Fluid D-Lactate – A Novel Pathogen-Specific Biomarker for the Diagnosis of Periprosthetic Joint Infection

Abstract Background Synovial fluid D-lactate may be useful for diagnosing periprosthetic joint infection (PJI) as this biomarker is exclusively produced by bacteria. We evaluated the performance of synovial fluid D-lactate using two definition criteria and determined its optimal cut-off value for diagnosing PJI. Methods Consecutive patients undergoing joint aspiration before prosthesis revision were prospectively included. Synovial fluid was collected for culture, leukocyte count and D-lactate concentration (by spectrophotometry). Youden's J statistic was used for determining optimal D-lactate cut-off value on the receiver operating characteristic (ROC) curve by maximizing sensitivity and specificity. Results A total of 224 patients were included. Using Musculoskeletal Infection Society (MSIS) criteria, 71 patients (32%) were diagnosed with PJI and 153 (68%) with aseptic failure (AF), whereas using institutional criteria, 92 patients (41%) were diagnosed with PJI and 132 (59%) with aseptic failure. The optimal cut-off of synovial fluid D-lactate to differentiate PJI from AF was 1.3 mmol/l, independent of the used definition criteria. Synovial fluid D-lactate had a sensitivity 94.3% (95% CI: 86.2-98.4%) and specificity 78.4% (95% CI: 66.8-81.2%) using MSIS criteria, while its sensitivity was 92.4% (95% CI: 84.9-96.9%) and specificity 88.6% (95% CI: 81.9-93.5%) using institutional criteria. The concentration of D-lactate was higher with Staphylococcus aureus (p Conclusion The synovial fluid D-lactate showed high sensitivity (>90%) for diagnosis of PJI using both definition criteria and correlated with the pathogen virulence. The high sensitivity makes this biomarker useful as a point-of-care screening test for PJI. Level of Evidence Diagnostic Level I.