Background: There are multiple sets of criteria used to define periprosthetic joint infection. The objective of this study is to compare the diagnostic accuracy of the calprotectin lateral flow point-of-care (POC) test in total knee arthroplasty (TKA) patients to diagnose infection using 3 different sets of criteria: (1) 2013 Musculoskeletal Infection Society, (2) 2018 Intentional Consensus Meeting (ICM), and (3) the 2019 proposed European Bone and Joint Infection Society criteria as reference standards.
Methods: From October 2018 to January 2020, 123 intraoperative synovial fluid samples were prospectively collected from revision total knee arthroplasty patients and tested using a calprotectin lateral flow POC assay. Data were reviewed and adjudicated by 2 independent reviewers blinded to calprotectin test results.
Results: The 3 criteria sets had 91.8% agreement. Using 2013 Musculoskeletal Infection Society criteria, the POC test demonstrated a sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and area under the curve (AUC) of 98.1%, 95.7%, 94.5%, 98.5%, and 0.969, respectively. Using the 2018 ICM, the POC test demonstrated a sensitivity, specificity, PPV, NPV, and AUC of 98.2%, 98.5%, 98.2%, 98.5%, and 0.984, respectively. Using the 2019 proposed European Bone and Joint Infection Society criteria, the POC test demonstrated a sensitivity, specificity, PPV, NPV, and AUC of 93.2%, 100.0%, 100.0%, 94.2%, and 0.966, respectively.
Conclusion: The calprotectin lateral flow POC test had excellent sensitivity and specificity across current available periprosthetic joint infection definitions, with the best performance observed when applying 2018 ICM criteria.
Level of evidence: Diagnostic I.
Keywords: PJI; calprotectin; periprosthetic joint infection; point-of-care test; revision total knee arthroplasty.
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