Neutrophil-to-lymphocyte ratio shows faster changing kinetics than C-reactive protein after total hip and knee arthroplasty.

BACKGROUND: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) induce inflammatory reactions, which can be described by changes in the neuroendocrine, cellular, protein, and cytokine systems. The aim of this study was to document the normal distribution pattern of the neutrophil-to-lymphocyte ratio (NLR) after THA and TKA and to compare it with postoperative C-reactive protein (CRP) patterns.

METHODS: Changes in serum CRP levels, neutrophil count, and lymphocyte count were measured before and during the first 5 postoperative days in a prospective study performed on 387 patients undergoing total hip or knee arthroplasty.

RESULTS: Mean CRP levels in patients undergoing THA were 7.7 mg/L, 184.8 mg/L, and 115.9 mg/L, respectively, at Days 0, 3 and 5. The mean NLR of patients undergoing THA was 2.9, 3.6, and 2.7, respectively, at Days 0, 3, and 5. Mean CRP levels in patients undergoing TKA were 7.8 mg/L, 192.6 mg/L, and 108.6 mg/L, respectively, at Days 0, 3 and 5. The mean NLR of patients undergoing TKA was 2.8, 3.4, and 2.6, respectively, at Days 0, 3, and 5. When comparing the preoperative value and the Day 3 value, CRP levels increased more than the NLR (almost a 24-fold increase in mean CRP values vs. a 1.2-fold increase in mean NLR values). In both groups, the NLR returned to preoperative values by the 5th postoperative day.

CONCLUSIONS: The present study demonstrated a significant elevation in CRP levels and the NLR following THA and TKA. In both groups, the NLR showed a faster kinetics pattern than CRP levels in response to surgical trauma. The translational potential of this article : We describe results of the use of the NLR, as compared to a routinely used marker, CRP, as advantageous in clinical setting due to faster dynamics of change. Integrating the NLR in clinical practice seems easy and without extra cost.