Ability of plasma-based or serum-based assays of D-dimer and FDP for diagnosing periprosthetic joint infection: protocol for a prospective single-centre, parallel comparative study

INTRODUCTION: Several studies have evaluated the diagnostic values of D-dimer and fibrin degradation product (FDP) for detecting periprosthetic joint infection (PJI), but their conclusions have been inconsistent. More importantly, whether the diagnostic value of these two biomarkers differs depending on whether they are assayed in plasma or serum is unclear. METHODS AND ANALYSIS: This prospective single-centre, parallel comparative study will involve patients planning to undergo revision hip or knee arthroplasty due to an aseptic mechanical failure or PJI. After the patients provide written informed consent, their serum and plasma will be sampled and assayed for D-dimer and FDP. The diagnostic value of these two biomarkers in plasma and serum will be compared with one another and with the value of two traditional inflammatory markers (C reactive protein and erythrocyte sedimentation rate) used to diagnose PJI according to the 2013 International Consensus Meeting criteria. Diagnostic value will be assessed in terms of area under receiver operating characteristic curves, sensitivity, specificity, as well as positive and negative predictive values, all calculated based on the optimal cut-off determined from the Youden index. ETHICS AND DISSEMINATION: This study was approved by the Ethics Committee of our hospital (approval no. 2020-859). Written informed consent will be obtained from all patients before enrollment. Study findings will be disseminated widely through peer-reviewed publications and conference presentations. TRIAL REGISTRATION NUMBER: This study was registered in the Chinese Clinical Trial Registry (ChiCTR2000038547), and it is ongoing. Title: