α-Defensin Accuracy to Diagnose Periprosthetic Joint Infection—Best Available Test?

BackgroundThe purpose of this study was to test the accuracy of a single synovial fluid biomarker, α-defensin, in diagnosing periprosthetic joint infection in revision total hip and revision total knee arthroplasty.MethodsA total of 102 patients comprising 116 revision total hip arthroplasty and revision total knee arthroplasty procedures performed between May 2013 and March 2014 were prospectively evaluated. Cases were categorized as infected or notinfected using Musculoskeletal Infection Society criteria. Synovial fluid was obtained and tested for α-defensin using a commercially available kit (Synovasure [CD Diagnostics, Baltimore, Maryland]).ResultsFor first-stage and single-stage revisions, the α-defensin test had a sensitivity of 100% (95% confidence interval [CI], 86%-100%) and a specificity of 98% (95% CI, 90%-100%) with a positive predictive value of 96% (95% CI, 80%-99%) and negative predictive value of 100% (95% CI, 93%-100%).ConclusionA positive α-defensin test result was significantly more sensitive and specific for predicting infection than current diagnostic testing and should be considered when managing periprosthetic joint infection.Level of Evidence: Level III, Study of Diagnostic Test.