The Role of Neutrophil-lymphocyte Ratio in the Diagnosis and Prognosis Evaluation of Sepsis: a Single-center, Retrospective Study

Neutrophil-lymphocyte ratio (NLR), as an inflammatory index, is cheap and easy to obtain, and could be widely used in hospitals at all levels. NLR is a valuable biomarker that is significantly correlated with the status of immune and inflammatory responses. In the past few years, NLR has been continuously and extensively explored in various diseases, and the research progress is considerable. In cardiovascular disease, NLR can predict arrhythmia and short - and long-term mortality in patients with acute coronary syndrome. NLR may be associated with heart failure and valvular heart disease. Moreover, NLR has been shown to be associated with respiratory diseases (such as chronic obstructive pulmonary disease), immune diseases (rheumatoid arthritis and systemic lupus erythematosus), and digestive diseases (acute appendicitis, hepatocellular carcinoma, liver fibrosis, and cirrhosis).Importantly, the study of NLR in sepsis has received much attention in recent years. A 2019 meta-analysis concluded that peripheral white blood cell ratios, including NLR, lymphocyte-to-monocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR), are associated with clinical outcomes in sepsis and are useful biomarkers of infection. They recommended that NLR be evaluated in future hierarchical models, To clarify its relationship with NLR and clinical outcome and the prognostic value of NLR, it is worth mentioning that NLR has also been found to have the ability to predict the outcome of sepsis. In 2019, Martins et al. and Westerdijk et al. came to a similar conclusion by analyzing two retrospective studies that NLR, together with other inflammatory parameters, might be a marker for early detection of sepsis in the intensive care unit. However, a large body of evidence demonstrating the association between NLR and adverse clinical outcomes in sepsis remains controversial. Another study concluded that "no association was found between NLR and 28-day in-hospital mortality in patients with sepsis". In addition, the reliability of NLR on admission in predicting the prognosis of critical illness was also lower than that of traditional markers (including CRP, PCT, serum lactic acid and APACHEⅡ score).

Inclusion Criteria:1.Patients with sepsis2.ICU stay time ≥3 days;Exclusion Criteria:1. History of solid organ or bone marrow transplantation;2. Diseases that may affect immune-related indicators, such as autoimmune diseases such as rheumatoid arthritis and SLE, or hematological malignancies such as leukemia and lymphoma;3. Have received radiotherapy or chemotherapy within the past 30 days, or have received immunosuppressive drugs (tripterygium, mycophenolate, cyclophosphamide, FK506, etc.), or have received continuous treatment with more than 10mg of prednisolone/day (or the same dose of other hormones);4. Pregnancy or lactation;c