Is leukocyte scintigraphy recommended in periprosthetic knee infection diagnosis? A retrospective study of 92 total knee arthroplasties

Purpose: The aim of this study was to assess in vitro labelled leukocyte scintigraphy (LS) diagnostic accuracy in periprosthetic knee infection diagnosis. Methods: This is a retrospective study that includes all patients with total knee arthroplasty (TKA) who performed LS before undergoing revision surgery for septic or aseptic loosening of the implant in our department from January of 2011 to March of 2023. The 2018 International Consensus Meeting (ICM) and 2021 European Bone and Joint Infection Society (EBJS) periprosthetic joint infection (PJI) definitions were employed to define infected and not infected patients. Results: 92 TKAs were included in this study. This was the LS diagnostic performance according to the 2018 ICM PJI definition: sensitivity 89%, specificity 80%, positive predictive value (PPV) 80%, negative predictive value (NPV) 89%, positive likelihood ratio (LR + ) 4.46, negative likelihood ratio (LR-) 0.14. According to 2021 EBJS PJI definition: sensitivity 91%, specificity 80%, PPV 76%, NPV 92%, LR + 4.43, LR- 0.12. Conclusion: Previously published studies on LS diagnostic performance report very variable results, probably due to the different and subjective PJI diagnostic criteria employed by each article. This is one of the first studies to employ the most recent PJI definitions and to demonstrate that LS may have a higher specificity and PPV than previously estimated. Therefore it represents a valid instrument in PJI diagnosis.