Abstract
BackgroundThe diagnosis of prosthetic joint infection (PJI) is still a challenge in some patients after total joint replacement. Interleukin-6 (IL-6) strongly participates in the arrangement of the host-bacteria response. Therefore, increased levels of IL-6 should accompany every PJI.PurposeThe aim of the study was to show diagnostic characteristics of serum IL-6 for the diagnosis of prosthetic joint infection (PJI). We also compared the diagnostic values of serum IL-6 with synovial IL-6 (sIL-6) and synovial C-reactive protein (sCRP).Study designWe performed a prospective study of 240 patients in whom serum IL-6 was determined before total hip (n = 124) or knee (n = 116) reoperations. The PJI diagnosis was based on the MSIS (Musculoskeletal Infection Society) criteria (2011). Receiver operating characteristic plots were constructed for IL-6, sIL-6, and sCRP.ResultsPJI was diagnosed in 93 patients, and aseptic revision was diagnosed in 147 patients. The AUC (area under curve) for IL-6 was 0.938 (95% CI; 0.904–0.971). The optimal IL-6 cut-off value for PJI was 12.55 ng/L. Positive and negative likelihood ratios for IL-6 were 8.24 (95% CI; 4.79–14.17) and 0.15 (95% CI; 0.09–0.26), respectively. The optimal sIL-6 and sCRP cut-off values were 20,988 ng/L and 8.80 mg/L, respectively. Positive and negative likelihood ratios for sIL-6 were 40.000 (95% CI; 5.7–280.5) and 0.170 (95% CI; 0.07–0.417), respectively. Negative likelihood ratio for sCRP was 0.083 (95% CI; 0.022–0.314).ConclusionsThe present study identified the cut-off values for serum/synovial IL-6 and synovial CRP for diagnostics of PJI at the site of THA and TKA and separately for each site. The diagnostic odds ratio for serum/synovial IL-6 and synovial CRP is very good. Simultaneous positivity of serum IL-6 either with synovial IL-6 or synovial CRP almost excludes false negative detection of PJI at the site of interest.
Highlights
Prosthetic joint infection (PJI) is a feared complication of total joint arthroplasty (TJA)
We compared the diagnostic values of serum IL-6 with synovial IL-6 and synovial C-reactive protein
The present study identified the cut-off values for serum/synovial IL-6 and synovial CRP for diagnostics of prosthetic joint infection (PJI) at the site of total hip arthroplasties (THA) and total knee arthroplasties (TKA) and separately for each site
Summary
Prosthetic joint infection (PJI) is a feared complication of total joint arthroplasty (TJA). Interleukin-6 (IL-6) is a soluble mediator expressed as part of host defense against a wide range of environmental stresses including microorganism invasion [4]. This is why it is one of the key cytokines, which is strongly up-regulated during septic inflammation. The most recent one of them concludes that serum IL-6 is less sensitive than the synovial fluid IL-6 test but still could have a value for patients with prosthetic failure due to its high specificity. The aim of the study was to show diagnostic characteristics of serum IL-6 for the diagnosis of prosthetic joint infection (PJI). We compared the diagnostic values of serum IL-6 with synovial IL-6 (sIL-6) and synovial C-reactive protein (sCRP)
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