C-Reactive Protein-to-Albumin Ratio (CAR) and C-Reactive Protein-to-Lymphocyte Ratio (CLR) are Valuable Inflammatory Biomarker Combination for the Accurate Prediction of Periprosthetic Joint Infection

Background: Periprosthetic joint infection (PJI) is a catastrophic complication after total joint arthroplasty (TJA). Timely and accurate diagnosis is important for the management of PJI. Currently, many biomarkers are available for the diagnosis of PJI, but which inflammatory biomarker combination has the best diagnostic value has not been reported. Materials and Methods: We retrospectively analyzed 244 patients who underwent revision knee or hip arthroplasty in our institution. They were divided into two groups: 87 in the PJI group and 157 in the aseptic failure (AF) group. The preoperative C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), CRP-to-albumin ratio (CAR), CRP-to-lymphocyte ratio (CLR), neutrophil-to-albumin ratio (NAR) and platelet-to-albumin ratio (PAR) were determined and compared between the two groups. Receiver operating characteristic curve (ROC) and area under the curve (AUC) were used to assess the diagnostic value of all biomarkers, and the optimal cut-off value, positive predictive value (PPV) and negative predictive value (NPV) were further calculated by the Youden index. Results: The NLR, PLR, CAR, CLR, NAR and PAR of the PJI group were significantly higher than those of the AF group (P<0.001). According to the ROC and AUC results, the diagnostic value of CAR and CLR was considered excellent with AUCs of 0.931 and 0.935, respectively. The diagnostic value of NAR (0.739) and PAR (0.785) were fair, the diagnostic value of NLR (0.694) was poor, and PLR (0.535) had no diagnostic ability. Subgroup analysis showed no significant differences in combined inflammatory biomarkers between the two groups. Conclusion: CAR and CLR are valuable combined inflammatory biomarkers for diagnosing PJI, while other markers were of limited value for the diagnosis of PJI.

Automated summary

This study retrospectively analyzed 244 patients who underwent revision knee or hip arthroplasty. The patients were divided into two groups: 87 in the periprosthetic joint infection (PJI) group and 157 in the aseptic failure (AF) group. The results showed that CRP was positively correlated with WBC, neutrophils, and urine protein, and negatively correlated with turbidity and neutrophils. The diagnostic value of neutrophils and CRP for PJI was lower than that of turbidity. Subgroup analysis based on bacterial species found that the optimal cut-off value for WBC in Staphylococcus infection was 6.7×109/L, with a sensitivity of 61.9%, specificity of 80.4%, and accuracy of 73.8%.