What Is the Diagnostic Performance and Accuracy of Serum Inflammatory Biomarkers and Synovial Fluid Analysis in Megaprosthetic Periprosthetic Joint Infections?

Abstract

Serum biomarkers and synovial fluid analysis are valuable tools for the preoperative diagnosis of periprosthetic joint infections (PJIs). However, the literature on their utility in megaprostheses is limited. Our study aimed to assess the diagnostic performance and accuracy of four laboratory tests for diagnosing PJI in patients who have megaprostheses. We retrospectively reviewed 104 patients who underwent 126 revisions after oncologic megaprosthesis reconstruction. Revisions were stratified into aseptic and septic according to the International Consensus Meeting criteria. The PJIs were classified into acute and chronic infections based on time since index surgery. There were four tests assessed: serum C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), synovial white blood cell (WBC) count, and polymorphonuclear percentage (PMN%). Receiver operating characteristic curve analysis was conducted to assess their performance. The diagnostic performance of preoperative tests in acute PJIs ranked by area under the curve was CRP (0.86), ESR (0.81), synovial WBC count (0.76), and synovial PMN% (0.69). In chronic PJIs, diagnostic performance ranked by area under the curve was synovial WBC count (0.80), CRP (0.77), ESR (0.71), and synovial PMN% (0.67). New cutoff values for diagnosing acute PJIs were identified as CRP ≥ 42 mg/L, synovial WBC count ≥ 5,500 cells/μL, and synovial PMN% ≥ 92.5%. For chronic PJIs, new cutoff values of CRP ≥ 31 mg/L, ESR ≥ 24.5 mm/hour, synovial WBC count ≥ 5,550 cells/μL, and synovial PMN% ≥ 76.5% were established. These cutoff values improved diagnostic accuracy in both acute and chronic PJIs. Good to excellent diagnostic performance was seen with all tests except synovial PMN%. Adjusting cutoff values in patients who have megaprosthesis revisions improved diagnostic performance.