The diagnostic accuracy of synovial leukocyte esterase, glucose and calprotectin in diagnosing periprosthetic joint infection

OBJECTIVES: Synovial leukocyte esterase, glucose and calprotectin have emerged as point-of-care biomarkers for diagnosing periprosthetic joint infections (PJI). Distinguishing chronic PJI from aseptic prosthetic failure remains challenging, yet accurate preoperative diagnosis is essential for optimal management and clinical outcomes. This study evaluates the diagnostic value of synovial leukocyte esterase, glucose and calprotectin in diagnosing chronic PJI using the European Bone and Joint Infection Society (EBJIS) criteria as the reference standard. METHODS: Synovial fluid was prospectively collected from patients undergoing revision arthroplasty. Leukocyte esterase and glucose were assessed with a standard urine dipstick, and calprotectin with a lateral flow immunoassay. Patients were excluded if they had prior antibiotic use, insufficient culture sampling, or missing histology analysis or synovial leukocyte counts. RESULTS: Eighty-eight patients were included. 30 patients were diagnosed with PJI (34%). The sensitivity, specificity, positive (PPV) and negative predictive value (NPV) of synovial leukocyte esterase with a cut-off value of ++ was 37%, 93%, 73% and 74%, respectively. The sensitivity, specificity, PPV and NPV of glucose with a cut-off value of - was 77%, 41%, 40% and 77%, respectively. The sensitivity, specificity, PPV and NPV of synovial calprotectin with a cut-off value of 50 mg/L were 77%, 88%, 77% and 88%, respectively. CONCLUSIONS: Using the EBJIS definition of PJI, synovial calprotectin showed superior diagnostic accuracy compared to synovial leukocyte esterase and glucose, highlighting its potential as a screening biomarker for chronic PJI. Synovial leukocyte esterase may serve as a specific confirmatory test, although a negative result does not exclude an infection.