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Periprosthetic joint infection (PJI) is a leading cause of total hip and knee arthroplasty failure. The Musculoskeletal Infection Society (MSIS) criteria for PJI has allowed diagnosis standardization. To increase the MSIS criteria accuracy, synovial fluid biomarkers have been tested. Studies evaluating synovial alpha defensin have reported both sensitivity and specificity up to 100%. In this study, we report our analysis on the use of alpha defensin testing in a suburban academic tertiary referral center.


We performed a retrospective analysis of a prospectively collected database of 133 patients tested for PJI over a 6 year period. From 2014, our standard infection evaluation protocol included synovial alpha defensin fluid analysis. Complete testing data was available on 128 patients. Both primary and revision total hip and knee arthroplasty were included. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated using the 2011 MSIS criteria. T-tests were performed for parametric data.


Synovial testing of alpha defensin for PJI had a 95.00% sensitivity, a 91.67% specificity, a 67.86% PPV and a 99.00% NPV. Positive alpha defensin tests were corelated with positive serum and synovial CRP, synovial WBC count, and synovial polymorphonuclear cell percent. There was no correlation between positive synovial alpha defensin and age, sex, smoking or diabetic status.


Synovial testing for alpha defensin in an unbiased cohort gives high sensitivity and NPV comparable to published literature. We recommend using synovial alpha defensin testing for suspected PJI cases, as an additional data point to help determine likelihood.