Diagnostic Value of Complete Blood Count Ratios in Identifying Periprosthetic Joint Infections: A Retrospective Cohort Study

Background: It is challenging to diagnose a periprosthetic joint infection (PJI) that frequently requires a combination of clinical and laboratory findings. Simple predictors of inflammation include the monocyte/lymphocyte ratio (MLR), neutrophil/lymphocyte ratio (NLR), platelet/lymphocyte ratio (PLR), and platelet/mean platelet volume ratio (PVR), all of which may be easily documented from a complete blood count. This study's objective is to search possible adjunctive diagnostic parameters to support Musculoskeletal Infection Society (MSIS) criteria(Table 1) in patients with suspected PJI, that are not costly, non-invasive, and helpful to non-gold standard diagnostic criteria. Methods: We compared the blood results of two patient groups a group of 66 patients with chronic periprosthetic joint infection who were scheduled for two-staged arthroplasty with those of a group of 65 arthroplasty patients with similar sociodemographic characteristics and without any complications. Results: According to the analysis results, a threshold value of > 2.26 for NLR and a threshold value of >29.5 for PVR in the preoperative period had the highest sensitivity (78.7 %), while a threshold value of > 0.35 for MLR in the preoperative period had the highest specificity (73.9%). Conclusion: Despite having moderate diagnostic accuracy NLR, PVR, and PLR were not considered as a useful diagnostic test to support the diagnosis of PJI. In conclusion, although NLR, PVR, and PLR showed moderate diagnostic accuracy, they were not reliable enough to serve as diagnostic tools for PJI. Further studies are warranted to explore their potential roles.