Neutrophil to lymphocyte ratio

Overview

The neutrophil-to-lymphocyte ratio (NLR) is a simple hematologic index calculated from routine blood counts as the ratio of circulating neutrophils to lymphocytes. It is widely used as a marker of systemic inflammation and immune balance. Because neutrophils often rise during acute inflammatory or stress responses while lymphocytes may decrease in states of immune suppression or physiologic stress, an elevated NLR is generally interpreted as reflecting a more pro-inflammatory and less adaptive immune profile.

Clinically, NLR has attracted attention as a low-cost, readily available biomarker in a broad range of diseases, including infection, cardiovascular and cerebrovascular disorders, autoimmune disease, and cancer. In recent biomedical research, it has been studied alongside other inflammatory indices such as the monocyte-to-lymphocyte ratio, platelet-to-lymphocyte ratio, systemic immune-inflammation index, and systemic inflammation response index. Its appeal lies in its accessibility and its potential to support prognostic stratification, risk prediction, and assessment of inflammatory burden.

Focus of Latest Publications

Recent studies have continued to evaluate NLR as a prognostic and diagnostic marker across diverse clinical settings. In acute cerebrovascular disease, a CLOT-VENUS substudy in acute cerebral venous thrombosis reported that inflammatory serum biomarkers, including NLR, were associated with functional outcomes. This places NLR among a group of immune-inflammatory markers considered relevant to early disease biology and recovery.

In respiratory infection, a study of community-acquired pneumonia described NLR as a simple index derived from routine blood counts and proposed it as a cost-effective prognostic marker for hospital outcomes. Similarly, in severe COVID-19, NLR was among the blood biomarkers statistically associated with coagulopathy, together with C-reactive protein, ferritin, fibrinogen, erythrocyte sedimentation rate, lactate dehydrogenase, and leptin, underscoring its use as part of a broader inflammatory-coagulation profile.

NLR has also been investigated in inflammatory and autoimmune conditions. In elderly patients with rheumatoid arthritis, researchers examined the relationship between geriatric nutritional risk index and immune-inflammatory biomarkers, including NLR, neutrophil-percentage-to-lymphocyte ratio, platelet-to-lymphocyte ratio, lymphocyte-to-monocyte ratio, and systemic immune-inflammation index, using data from NHANES. In drug-resistant epilepsy, elevated NLR was part of a systemic immune dysregulation signature characterized by increased C-reactive protein, proinflammatory cytokines such as interleukin-6, CXCL8/IL-8, and TNF-α, and activated neutrophils. These findings suggest that NLR may reflect broader inflammatory activation beyond classical infectious or Malignant Disease.

In oncology, NLR has been repeatedly studied as a prognostic or diagnostic variable. It was reported as an independent predictor of malignant thyroid nodules in a nomogram model combining ultrasound features and blood inflammatory indicators. In osteosarcoma, NLR was evaluated for prognostic significance alongside systemic inflammation response index and prognostic nutritional index, with attention to clinicopathological factors. In bladder cancer, high-risk patients showed elevated NLR together with increased circulating regulatory T cells and reduced cytotoxic γδ T cells and Th1/Tc1 functional subtypes, consistent with systemic immunosuppression. In metastatic renal cell carcinoma, NLR was incorporated into the Meet-URO score, which also includes IMDC classification and bone metastases, and was externally validated in Japanese patients receiving first-line immune-combination therapy. In remnant gastric cancer, NLR was included in the cachexia index, a composite prognostic indicator incorporating skeletal muscle mass and serum albumin. In non-small cell lung cancer, early-phase human studies of bronchoscopic cryoimmunotherapy reported reductions in the derived NLR alongside expansion of CD8+ effector memory populations, suggesting treatment-associated immune stimulation.

NLR has also been used in non-human and non-oncologic settings. In cats with feline panleukopenia virus, NLR was higher in a treatment group receiving inactivated parapoxvirus ovis and combined filgrastim therapy, compared with other groups, indicating its utility as a comparative inflammatory marker in veterinary medicine. In hemodialysis patients with end-stage renal disease and suspected acute cholecystitis, NLR was among several systemic inflammatory indices calculated for diagnostic evaluation. Across these studies, NLR consistently served as a practical surrogate of inflammatory and immune status, often interpreted in relation to outcomes, disease severity, or treatment response.

Key Publications

• Jun Early Inflammatory Biomarkers Associated With Functional Outcomes in Acute Cerebral Venous Thrombosis: CLOT-VENUS Substudy. (Stroke, 2026, PMID 42017277): "Inflammatory serum biomarkers, including neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), and systemic immune-inflammation index (SII), are associated with outcomes in acute cerebrovascular diseases."
• May Predictive value of neutrophil-to-lymphocyte ratio on hospital outcomes of patients with community-acquired pneumonia. (PloS one, 2026, PMID 42213696): "The neutrophil-to-lymphocyte ratio (NLR), a simple index derived from routine blood counts, has been proposed as a cost-effective prognostic marker."
• May Diagnostic utility of systemic inflammatory markers for acute cholecystitis in hemodialysis patients with end-stage renal disease. (Medicine, 2026, PMID 42175491): "Systemic inflammatory indices, including the neutrophil-to-lymphocyte ratio, systemic immune-inflammation index, systemic inflammation response index (SIRI), and pan-immune-inflammation value (PIV), were calculated."
• May The value of a nomogram model combining ultrasonic features and blood inflammatory indicators in differentiating benign and malignant thyroid nodules. (Medicine, 2026, PMID 42175458): "...neutrophil-to-lymphocyte ratio (OR = 4.23) was an independent predictor of malignant thyroid nodules (all P < .05)."
• May The association between geriatric nutritional risk index (GNRI) and immune-inflammatory biomarkers in elderly rheumatoid arthritis: Insights based on NHANES 2005-2018. (Medicine, 2026, PMID 42175440): "This study aimed to explore the relationship between geriatric nutritional risk index (GNRI) and immune-inflammatory biomarkers neutrophil-percentage-to-lymphocyte ratio (NPAR)/neutrophil-to-lymphocyte ratio (NLR)/platelet-to-lymphocyte ratio (PLR)/lymphocyte-to-monocyte ratio (LMR)/systemic immune-inflammation index (SII) in elderly RA patients."
• May Systemic immune dysregulation and neutrophil activation define prognostic inflammatory signatures in drug-resistant epilepsy. (JCI insight, 2026, PMID 41979892): "...characterized by elevated neutrophil-to-lymphocyte ratio, C-reactive protein, proinflammatory cytokines (IL-6, CXCL8/IL-8, TNF-α), and activated neutrophils (CXCR4+CD62Llo)."
• May Investigation of the prognostic effects of inactivated parapoxvirus ovis and combined filgrastim therapy in naturally infected cats with feline panleukopenia virus. (Acta veterinaria Hungarica, 2026, PMID 41670620): "Group C showed significantly higher levels of white blood cells (WBC), neutrophils (NEU), lymphocytes (LYM), monocytes (MON), neutrophil-to-lymphocyte ratio (NLR) and systemic inflammatory response index (SIRI) compared to other groups."
• May Potential of Inflammatory and Nutritional Markers and Clinicopathological Factors for Prognostic Prediction in Osteosarcoma. (Anticancer research, 2026, PMID 42049341): "This study evaluated the prognostic significance of the neutrophil-to-lymphocyte ratio (NLR), systemic inflammatory response index (SIRI), and prognostic nutritional index (PNI), and examined their associations with clinicopathological factors."
• May Cross-talk between inflammation and coagulation in severe COVID-19: Association of leptin and classical pro-inflammatory markers with coagulation disorders in a single-center observational cohort study. (Medicine, 2026, PMID 42065184): "We found statistically significant associations between blood levels of various biomarkers including leptin, IL-6, ferritin, neutrophil-lymphocyte ratio, C-reactive protein, fibrinogen, erythrocyte sedimentation rate and lactate dehydrogenase and the presence of coagulopathy, as indicated by the Pearson Chi-Square and Likelihood Ratio tests."
• May The association of systemic inflammatory indices with all-cause mortality risks in patients with COPD: A cohort study based on machine learning. (Medicine, 2026, PMID 42065179): "The neutrophil percentage-to-albumin ratio (NPAR) and neutrophil-to-lymphocyte ratio exhibited the strongest associations, with HRs of 2.46 (95% CI: 1.64-3.69) and 2.14 (95% CI: 1.42-3.22), respectively, in the highest quartile (Q4) compared to the lowest (Q1)."