Counting the number of neutrophils and dividing by the number of lymphocytes, a ratio termed the neutrophil to lymphocyte ratio (NLR), is one way to measure inflammation within the body.
When there are high neutrophils and low lymphocytes, the NLR is high. This indicates that the body is under stress and is a sign of certain medical conditions.
Neutrophils and Lymphocytes in Inflammation
Neutrophils are the first responders in inflammation and they quickly arrive on the scene and get to work in a process known as innate immunity. Lymphocytes have a slower but still important response to inflammation and tend to arrive after neutrophils as part of the adaptive immune response.
The NLR works based on the knowledge that increasing levels of stress hormones produced by the body will drive the neutrophil levels up and the lymphocyte levels down. As a result, this ratio can be a marker that reflects the stress levels that the body is experiencing during acute illness.
The changes in neutrophil and lymphocyte cell levels have been associated with the severity of illness in a variety of conditions including infections, cancer, and even major cardiovascular events.
How Do You Measure the NLR?
Measuring levels of white blood cells is done using a common blood test called a complete blood count (CBC), which can identify the specific types of white blood cells circulating in the blood. When a complete blood cell count with differential is performed, the instrument used can identify and count neutrophils and lymphocytes.
The NLR ratio provides insight into the inflammatory status of the body. A normal NLR will generally fall between a level of 1 to 4, though this value may vary from person to person.
An NLR level above 6 is considered an indicator of severe inflammation. In severe illness, the NLR may go as high as 100.
What Are the Risks of an Elevated NLR?
During episodes of stress, such as when the body is responding to an infection, the NLR can become abnormally elevated and climb to levels as high as 100. There are many potential causes of an elevated NLR. As a result, the NLR is used most often as a way to evaluate the severity of disease and how the body may be responding to infection.
For example, the NLR is associated with severe infection with COVID-19 and other infectious diseases. In some studies, an elevated NLR was able to identify individuals likely to have more severe cardiovascular and respiratory diseases.
The NLR may be most useful for predicting the severity of infection. Studies have shown that using the NLR in a hospital emergency department may aid in identifying and more promptly treating bloodstream infections, known as bacteremia.
This number can be used to assist in the diagnosis of appendicitis (inflammation of the appendix, the tube-shaped pouch on the right side of the abdomen that extends from the large intestine). An elevated NLR has been shown to correspond to the severity of appendicitis and may be useful in determining the need for surgery.
Conditions with an elevated NLR include:
Sepsis (a possibly life-threatening whole-body inflammatory response to an infection) Bacteremia (bloodstream infection) Septic shock (low blood pressure in response to sepsis) Pancreatitis (inflammation of the pancreas) Appendicitis (inflammation of the appendix) Cancer Inflammatory disorders such as Crohn’s disease and ulcerative colitis (types of inflammatory bowel disease) Autoimmune disorders like rheumatoid arthritis Asthma (a chronic lung disease making breathing difficult) and allergies (immune reaction to substances that are usually harmless)
It is important to note that the NLR is just one measure and a full evaluation in the context of the specific disease is necessary before making any decisions.
Cancer
Some studies have also investigated the role of the NLR in the prognosis of people with cancer undergoing chemotherapy treatment. The NLR is a predictor of adverse outcomes like weight loss and cachexia (weight loss and muscle wasting) in people undergoing chemotherapy.
An elevated NLR is associated with an adverse prognostic and a decreased overall survival in many solid tumors regardless of the type and stage.
Interpreting High Neutrophils With Low Lymphocytes
The neutrophil to lymphocyte ratio is a relatively new measure of inflammation within the body that is still gaining acceptance. Growing clinical evidence has highlighted the utility of this measure, however, it may not always apply to every disease.
Interpretation of the NLR in the context of other laboratory and blood tests is needed in order to properly assess the body’s response to acute illness. For this reason, measuring the NLR should be done with the assistance of a healthcare provider who can help interpret the findings alongside other measures.
In some cases, the NLR may not be accurately measured. For example, certain cancers such as leukemias may skew the measurement of the NLR. In addition, certain treatments such as chemotherapy or bone marrow or stem cell transplants can also alter the NLR and limit its predictive ability.
Summary
High neutrophils and low lymphocytes together represent an elevated NLR ratio. The elevation can be caused by many different conditions and may be an indicator of a severe infection, an inflammatory disorder, or cancer.
High levels of neutrophils may indicate a severe infection or stress on the body. Low levels of lymphocytes may also reflect severe stress and the release of stress hormones.
A Word From Verywell
If you see high neutrophils and low lymphocytes on your lab report, discuss this finding with your healthcare professional. While it may indicate inflammation, it needs to be interpreted with consideration of your overall health, symptoms, and other diagnostic findings. As with any lab test, it is only one tool in diagnosing illness.
