Predictive value of postoperative neutrophil-to-lymphocyte ratio on the early Periprosthetic joint infection after total joint arthroplasty: a pilot study

Objective : The purpose of this study was to evaluate the predictive value of the postoperative neutrophil-to-lymphocyte ratio on early periprosthetic joint infection. Methods : During the period from January 2008 to December 2016, 104 patients (26 early PJI cases and 78 non-PJI cases) who underwent total joint arthroplasty in the department of orthopedics in our Hospital were enrolled in our study. All of the relevant clinical information and laboratory indexes were reviewed from the our Hospital Follow-up system. The time when any abnormal symptoms or signs occurred including fever, local swelling or redness around the surgical site 2 weeks after the operations was defined as the “suspect time”. We compared the laboratory parameters including the NLR 、PLR、LMR、ESR and the CRP between the two groups. The trend of the NLR、LMR、PLR、CRP and ESR were also reviewed after the surgery. The predictive ability of these parameters at suspect time on the early PJI were evaluated by multivariate analysis and the Receiver operating curve analysis (ROC). Results : NLR, PLR and LMR returned to preoperative level within two weeks in two groups after surgery. In the early PJI group, NLR and PLR were significantly increased during the incubation period of infection or infection, LMR was significantly reduced, although 61.5% (16/26) of the patients had normal white blood cell. Interesting, the ESR and CRP were still in relative high level two weeks after the operation and the change of these two indexes was not obvious when the infection occurs. The NLR and PLR was significantly correlated with the early PJI (OR NLR =88.36, OR PLR =1.12, P NLR =0.005, P PLR =0.01) and the NLR has a great predict ability for early PJI with the cut-off value 2.77 (Sensitivity=84.6% ，Specificity=89.7%, 95% CI=0.86-0.97) Conclusions: ESR and CRP are not sensitive for diagnosis of early PJI due to their persistent high level after arthroplasty. The postoperative NLR at suspect time have a great ability in predicting early PJI and more attention should be applied to it.