Neutrophil–Lymphocyte Ratio as a Predictor of Venous Thromboembolism after Total Knee Replacement

Venous thromboembolism (VTE) is a potentially serious complication after total knee replacement (TKR), and recent guideline recommends thromboprophylaxis for VTE after TKR. The neutrophil–lymphocyte ratio (NLR) has emerged as a simple and new prognostic biomarker for several cardiovascular diseases. This study was performed to investigate the precise incidence of postoperative VTE and the role of NLR for predicting VTE in patients receiving thromboprophylaxis after TKR. We retrospectively enrolled 264 patients undergoing TKR who underwent routine screening enhanced pulmonary artery and lower extremity venography computed tomography (CT) scan within 7 postoperative days. Biochemical tests were performed within 2 weeks prior to surgery, and the NLR was defined as the absolute neutrophil count in peripheral blood divided by lymphocyte count. All patients received thromboprophylaxis with enoxaparin postoperatively. Of 264 patients, 102 (38.6%) were diagnosed with deep vein thrombosis (DVT) or pulmonary embolism on CT scan. Preoperative NLR was significantly higher in patients with postoperative VTE compared with that in patients without VTE (2.57 ± 1.59 vs. 2.11 ± 1.10, p = 0.011). Receiver operating characteristic curve analysis showed that a preoperative NLR of 1.90 was the best cutoff value for the prediction of postoperative VTE (sensitivity 57.8%, specificity 55.6%, and area under curve 0.589). In the multivariate analysis, a preoperative NLR ≥1.90 was a sole independent predictor of postoperative VTE (odds ratio: 1.95, 95% computed tomography: 1.16–3.31, p = 0.013). The present study shows a higher incidence of VTE (38.6%) after TKR in patients receiving thromboprophylaxis than that reported in previous studies. Furthermore, preoperative NLR was significantly higher in patients with postoperative VTE, and a high preoperative NLR (≥1.90) was an independent predictor of VTE after TKR. NLR measurement may be a simple and useful method for the prediction of VTE in patients undergoing TKR.