Evaluation of neutrophil/lymphocyte ratio as a potential biomarker to determineinfections in renal transplant recipients

In renal transplant recipients, post-transplant infections are the most common complication and major cause of mortality, morbidity, and graft loss. Early detecting and preventing infections is one of the most important factors to improve survival. We aimed to analyze the infection-related emergency visits and evaluate the value of neutrophil- lymphocyte ratio (NLR) predicting infections in renal transplant recipients as a cost- effective, rapid, and accessible laboratory biomarker. We retrospectively reviewed the medical records of renal transplant recipients who presented to our emergency department with infection-related symptoms during a 5-year period; 2015 to 2020. Our analysis included 283 patients in case group which laboratory results were available and the source of infection was determined. We compared results with a control group of 245 transplant patients without any infectious symptoms who applied to the General Surgery Department and Transplantation Unit of our hospital for routine control within the time period we determined. The study data was analyzed with SPSS for Windows v20.0 software, and p values <0.05 were considered statistically significant. The mean age was 42.42±12.96 and 63.6% (180/283) of the patients were male in the case group. The most common cause of infections in the case group were urinary tract infections (86/283; 30.4%), and the frequency was higher in women (46.6% vs. 21.1%; p<0.001). In addition, upper respiratory tract infections were more common in men (36.1% vs 19.4%; p=0.003). Leukocytes, neutrophils, C-reactive protein (CRP), NLR and platelet/lymphocyte ratio (PLR) were higher in the case group than in the control group (p<0.001). On the other hand, platelet, lymphocyte, and Red Cell Distribution Width (RDW) values ​​were lower (p<0.05, <0.001, and <0.001, respectively). The median NLR was 7.11 (IQR: 6.81) in case group, and the area under the ROC curve (AUC: 0.876; 95% CI: 0.845-0.906) for any diagnosis of infection of the NLR was statistically significant (p<0.001). The cut-off value for NLR at increased risk of any infection was calculated as 3.30, with a sensitivity of 84% (95% CI; 80%-88%) and specificity of 77% (95% CI; 71%- 81%). Pneumonia was the disease group with the highest diagnostic performance of NLR with 93% sensitivity and 87% specificity. The NLR cut-off value of NLR associated with the diagnosis of pneumonia was 4.29, and the area under the ROC curve was the highest 7 for pneumonias (AUC: 0.953; 95% CI: 0.925-0.981; p<0.001). According to our Multivariate Logistic Regression Analysis, renal transplant recipients with NLR>3.3 had a 2.8-fold increased risk of developing any infection (p=0.013). Age, female gender, and PLR values ​​were not found to be independent risk factors for the development of infection in renal transplant recipients (p>0.05). In conclusion, we found a significantly higher NLR in emergency visits of infection-related origin of renal transplant recipients than in the control group (p<0.001), and NLR was an independent risk factor over the cut-off value of 3.3 for any infectious disease in RT recipients (OR: 2.808; 95% CI: 1.246-6.326; p=0.013), so we suggested that NLR is an available, rapid, cost-effective and reliable biomarker of infections which is the most significant complication of a post-transplantation period.