The diagnostic accuracy of neutrophils to lymphocytes ratio, platelets to lymphocytes ratio, monocytes to lymphocytes ratio, and platelets to mean platelet volume ratio in diagnosing periprosthetic knee infections. Are gender specific cut-off values needed?

Abstract

Introduction

This study aimed to assess the most appropriate thresholds for neutrophils to lymphocytes ratio (NLR), platelets to lymphocytes ratio (PLR), monocytes to lymphocytes ratio (MLR), and platelets to mean platelet volume ratio (PVR) in patients who had a suspected prosthetic knee infection. Furthermore, we evaluated the diagnostic accuracy of our proposed thresholds by men and women.

Methods

A total of 261 consecutive patients affected by painful total knee arthroplasty were included. International Consensus Meeting diagnostic criteria were used to identify periprosthetic infections. Sensitivity, specificity, positive, and negative predictive values were calculated for each cut-off value obtained. The area under the receiver operating characteristic (ROC) curve was evaluated.

Results

NLR reported the best diagnostic accuracy. MLR and NLR reported higher area under the curves (AUCs) in men and women. We obtained a MLR value ≥ 0.30 (optimal cut-off value for men) and ≥ 0.17 (optimal cut-off value for women). In men, the sensitivity and the specificity were 0.71 and 0.77, respectively, versus 0.82 and 0.29, in women. For NLR we obtained a value ≥ 2.52 (best cut-off value for men) and ≥ 2.46 (best cut-off value for women). These cut-offs reported a sensitivity and specificity of 0.71 and 0.88 versus 0.54 and 0.76 in men and women, respectively.

Conclusion

These biomarkers present a low diagnostic accuracy in PJI detection. Men whose MLR and NLR were above cutoff values had a 77 and 88% probability of presenting a septic prosthetic failure. NLR of at least 2.46 was reasonably sensitive for women who have a periprosthetic knee infection.