Blood tests that show low lymphocytes and high neutrophils indicate that the body is under stress and can be a sign of certain medical conditions. Neutrophils and lymphocytes are types of white blood cells that play a critical role in protecting the body from infections, among other roles.
White blood cells are a key component of the body’s response to physical stress, and they coordinate the process known as inflammation. 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.
This article explains the NLR and how it is measured. It discusses the way results are used and the types of conditions that may be diagnosed, based on factors that include the NLR.
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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 release of natural stress hormones regulates the levels of neutrophils and lymphocytes within the body. These hormones help the body initiate the inflammatory response and respond to and fight infection, cancer, and other diseases.
The NLR is based on the knowledge that neutrophil levels go up and 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
- Major cardiovascular events
What Does It Mean When Lymphocytes Are Low?
The lymphocytes are a specific population of white blood cells. They play a crucial role in fighting infections, producing immunity, and controlling abnormal cells in our body. When the lymphocyte levels are low, the body may be experiencing severe stress.
How the Immune System Works
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 Is Considered a High Neutrophil Count?
In adults, a normal neutrophil count falls between 2,500 to 6,000 neutrophils per microliter. A neutrophil count higher than this is considered elevated.
Causes 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.
Acute bacterial infections, such as pneumococcal,staphylococcal, or leptospiral infections, are the most common cause of high neutrophils. Certain viral infections can also cause high neutrophils, such as herpes complex and varicella (chickenpox) infections.
Dehydration and malnutrition are possible causes of low lymphocytes (lymphopenia). However, the NLR is more associated with viruses and severe infectious diseases, like COVID-19. In some studies, an elevated NLR was able to identify individuals likely to have more severe cardiovascular and respiratory diseases.
Conditions Associated With an Elevated NLR
The NLR 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.
In addition to those previously mentioned, specific conditions seen with an elevated NLR include:
- Sepsis (a possibly life-threatening whole-body inflammatory response to an infection)
- Septic shock (low blood pressure in response to sepsis)
- Pancreatitis (inflammation of the pancreas)
- 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 makingbreathing 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 evaluationin the context of the specific disease is necessary before making any decisions.
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.
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.
Interpretation of the NLR in the context of other laboratory and blood tests is needed 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.
Mortality and NLR
High neutrophils are not a reliable indicator of cancer, and diagnosis relies on blood tests, imaging, and testing of organ tissue (biopsy).However, elevated NLR has been associated with increased morbidity and poor survival in people with cancer, regardless of the type and stage, as well as in those with chronic liver and cardiovascular disease.
Should I Worry About High Neutrophils and Low Lymphocytes?
NLR is a generally recognized marker of disease severity and correlates with mortality both in the general population and in association with specific diseases (sepsis, pneumonia, COVID-19, cancer, etc.). In adults, normal values of NLR are between 1-2 with values higher than 3.0 or below 0.7 associated with poor health and disease.
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.
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.
