Diagnosing periprosthetic infection with C-reactive protein in joint fluid

Background The diagnosis of Periprosthetic Joint Infection (PJI) is a considerable challenge in total joint arthroplasty. The mainstay for diagnosis of PJI is a combination of serological markers, including C-reactive protein (CRP), along with joint aspirate for white cell count, differential and culture. The aim of this study was to examine the use of synovial fluid CRP in the diagnosis of PJI. Material & Methods Synovial fluid samples were collected prospectively from patients undergoing primary and revision knee arthroplasty. Samples were assessed for CRP, cell count and differential. Three groups were analyzed; those undergoing primary knee arthroplasty, aseptic knee arthroplasties and infected arthroplasties. Demographic data, along with associated medical co-morbidities, were collected,. Statistical analysis was performed. Synovial fluid CRP was correlated with serum CRP values. Sensitivity and specificity were calculated. Results 50 synovial fluid samples were collected from 50 patients. Synovial fluid CRP was 0.3 +/− 0.4 in native knees, 0.2 +/− 0.5 in aseptic knee arthroplasties, 4.3+/−4.1 in patients with infected knee arthroplasties. Synovial fluid CRP was significantly higher in septic total knee arthroplasties by comparison to both aseptic total knees (p Conclusion While this is preliminary data, synovial fluid CRP was found to be significantly elevated in patients with infected total knee arthroplasties. This test is easily performed under routine hospital laboratory conditions without specific, expensive assays. We believe synovial CRP assay holds great promise as a new, potentially low-cost, diagnostic marker for PJI.