- Neutrophil-to-lymphocyte ratio in cats as a prognostic marker for blunt trauma
- What is the neutrophil-to-lymphocyte ratio in cats?
- 🔬 How is the NLR determined in cats?
- 🐾 When is it advisable to determine the NLR in cats?
- 📊 Categorization of the NLR in cats
- 📊 Decision tree: NLR determination in cats
- Here are 5 frequently asked questions (FAQ) about the neutrophil-to-lymphocyte ratio (NLR) in cats.
- Summary of neutrophil-to-lymphocyte ratio in cats
- Further sources:
Neutrophil-to-lymphocyte ratio in cats as a prognostic marker for blunt trauma
A current retrospective study with 177 cats This shows that the neutrophil-to-lymphocyte ratio (NLR) could be a valuable early indicator of the extent of trauma and the severity of the inflammatory response. This ratio, which has already been associated with survival prognosis in human medicine, is also gaining increasing importance in veterinary medicine.
The study included blood tests performed within 24 hours of the trauma and thoracic X-rays. The results are striking: cats with blunt trauma had a significantly higher mean NLR (8.4) than healthy control animals (2.3). The difference was particularly noticeable in cases of thoracic injury – here, the average NLR was 9.2, compared to 6.4 in injured cats without thoracic trauma.
A threshold of 4.45 proved particularly reliable for distinguishing between healthy and injured cats – with a sensitivity of 74 % and a specificity of 71 %. Even more interesting: The NLR correlated directly with the Animal Trauma Triage (ATT) score. The more severe the injury, the higher the NLR – from 3.98 (mild) through 13.1 (moderate) to 28.2 (severe).
However, the authors warn that automated leukocyte counts can be misleading, as immature neutrophils (band cells) could be incorrectly identified as lymphocytes. Therefore, a manual differential blood count is recommended – especially in cases of abnormal or borderline results.
These findings provide valuable insights for emergency and intensive care medicine in cats. An elevated NLR can help to quickly assess the severity of a trauma – and thus plan further treatment more effectively.
What is the neutrophil-to-lymphocyte ratio in cats?
The Neutrophil-to-lymphocyte ratio (NLR) is an easy-to-determine laboratory parameter that reflects the ratio of two important white blood cells in peripheral blood: Neutrophils and Lymphocytes. Both cell types play a central role in the immune system, but fulfill different tasks:
- Neutrophils They are part of the innate immune response and are rapidly mobilized in large numbers during acute inflammatory reactions, infections, and tissue damage. They are, so to speak, the body's "first line of defense".
- Lymphocytes In contrast, they belong to the specific, acquired immune system. They are essential in fighting viruses, in the formation of antibodies, and in the long-term immune response.
The NLR The NLR is simply calculated by dividing the number of neutrophils by the number of lymphocytes. For example, if a patient has 7000 neutrophils and 2000 lymphocytes per microliter of blood, the NLR is 3.5.
What is the NLR used for in human medicine?
In human medicine, the neutrophil-to-lymphocyte ratio has changed in recent years to become a promising prognostic markers developed – primarily because it is fast, inexpensive and included in almost every blood test.
1. Inflammation and infection
An elevated NLR can indicate a systemic inflammatory response. Therefore, it is often considered Markers for inflammatory activity It is used – for example in cases of sepsis, appendicitis, bacterial infections, or even COVID-19. Studies have shown that patients with a high NLR in COVID-19 had a higher risk of a severe course.
2. Cardiovascular diseases
A high NLR was associated with a worse prognosis in patients with heart attack, Heart failure or stroke It is associated with this. It is considered a marker for the inflammatory status and the severity of the event.
3. Oncology (cancer medicine)
The NLR is also receiving increasing attention in cancer medicine. Numerous studies show that an elevated NLR is associated with a poorer prognosis in many types of tumors – including lung cancer, colorectal cancer, breast cancer, and pancreatic cancer. In these cases, a high NLR level indicates a tumor-associated inflammatory response that could promote tumor growth and metastasis.
4. Surgery and Intensive Care
In preoperative assessment as well as in critically ill patients in intensive care units, an abnormal NLR can indicate Complications or indicate an increased risk of death. It helps to identify high-risk patient groups early on.
Why is the NLR so interesting?
What makes the NLR special is its Easily accessible messageIt is derived from a standard blood test, which is performed on almost every hospitalized patient anyway. Therefore, no additional test is necessary. At the same time, it provides a quick insight into the balance between acute inflammation and specific immune response, which can be very helpful, especially in cases of acute illness or trauma.
Human medicine has already recognized the potential of the NLR – and now veterinary studies are also showing that this relationship It also plays a valuable diagnostic and prognostic role in animals. could play.
The Determination of the neutrophil-to-lymphocyte ratio (NLR) In cats, it is a simple but extremely useful diagnostic tool that is gaining increasing attention in veterinary practice – especially in the assessment of acute illnesses, injuries or systemic inflammations.
🔬 How is the NLR determined in cats?
The NLR is calculated based on a Complete Blood Count (CBC). This blood test can be performed either using an automated hematology analyzer or manually. Among other things, the following are included: Numbers of different white blood cells (Leukocytes) are differentiated and recorded – including in particular:
- Neutrophils (also subdivided into rod-shaped and segmented cores)
- Lymphocytes
The actual calculation of the NLR is very straightforward: NLR = Number of neutrophils / Number of lymphocytes
Example: If a cat has 8000 neutrophils/μl and 2000 lymphocytes/μl, the NLR is: NLR = 8000 2000 = 4.0 NLR = 8000/2000 = 4.0 NLR = 2000 8000 = 4.0
Important: The accuracy of the result depends on whether the cell counts were determined reliably. Automated devices can produce erroneous results in abnormal blood counts, for example, if immature neutrophils (band cells) are mistakenly identified as lymphocytes. Therefore, manual differentiation is always recommended in case of abnormalities. by an experienced laboratory technician or veterinarian.
🐾 When is it advisable to determine the NLR in cats?
Determining the NLR level can be useful in many clinical situations. provide valuable information about a cat's health, especially when it comes to better assessing the severity of an illness or trauma:
✅ 1. In case of blunt trauma
As recent studies show, the NLR (nitrogen renin receptor) is often significantly elevated in cats with blunt injuries (e.g., falls from a great height, traffic accidents). The higher the NLR value, the stronger the inflammatory response appears to be – which allows conclusions to be drawn about the Extent of injury and the need for intensive medical care is permitted.
✅ 2. In case of suspected systemic inflammation or infection
An elevated NLR can indicate a systemic inflammatory response These findings can indicate, for example, bacterial infections, abscesses, sepsis, or other inflammatory processes. In conjunction with other blood parameters (e.g., fever, CRP, fibrinogen), a comprehensive picture of the immune status can be obtained.
✅ 3. In the case of chronic illnesses or cancer
In human medicine, the NLR is an established marker for assessing the prognosis of tumor diseases. This is also being increasingly researched in veterinary medicine. In cats with lymphoma, carcinomas, or other neoplasms, an abnormal NLR may indicate a Tumor-associated inflammatory response indicate.
✅ 4. For monitoring progress
The NLR can also be used for Monitoring of disease progression or therapies This can be used. If the ratio decreases during the course of treatment, this can be an indication of improvement; if it increases, the therapy should be adjusted or complications investigated.
🧠 What should be considered when interpreting the text?
- The NLR is no isolated marker, but should always be considered in the context of clinical symptoms and other laboratory values.
- Normal ranges can vary depending on the laboratory and equipment settings. In studies, NLR values in healthy cats were in the range of approximately 2 to 3 – significantly lower values than in traumatized or sick cats.
- Stress (e.g. Veterinary visit) can lead to a temporary increase in neutrophils and a decrease in lymphocytes in cats – which temporarily increases the NLR without any serious illness being present.
Determining the neutrophil-to-lymphocyte ratio in cats is fast, easy and cost-effective —and yet offers a wide range of diagnostic possibilities. Whether in acute emergencies, chronic illnesses, or for monitoring disease progression: the NLR can help, to better assess a cat's condition, support decisions, and evaluate prognoses more accurately.. When used correctly, it is a valuable tool in everyday veterinary practice.
To do this Neutrophil-to-lymphocyte ratio (NLR) To make practical use of this method in cats, it is helpful to interpret the measurement results in Categories to classify. Even though there are currently no internationally standardized norms for cats (as is sometimes the case in human medicine), current studies – such as those by Doulidis et al. (2024) – good starting points for an initial assessment.
Below you will find a clear table about Categorization of NLR values in cats, based on the current state of knowledge from literature and clinical practice:
📊 Categorization of the NLR in cats
| NLR value | interpretation | Possible meaning |
|---|---|---|
| < 3.0 | Normal range (reference value for healthy cats) | Healthy cat, no signs of acute inflammation or stress reaction |
| 3.0 – 5.0 | Slightly increased | Mild inflammatory reaction, stress response, early stage of disease possible |
| 5.1 – 10.0 | Moderately increased | Possible indication of systemic inflammation, trauma, or infection |
| 10.1 – 20.0 | Significantly increased | Significant inflammatory response, trauma with complications, severe infection |
| > 20.0 | Significantly elevated / critical | Possibly severe systemic illness, sepsis, very high level of inflammation |
💡 Instructions for use:
- An NLR over 4.45 In the study by Doulidis et al., this was considered a threshold with good sensitivity and specificity for distinguishing between injured and healthy cats.
- Cats with thoracic trauma showed particularly high NLR values (median 9.2), while severely injured cats (ATT score >8) even showed values up to over 28.0.
- stress (e.g., through transport or handling) can temporarily increase the ratio, so this should be taken into account when interpreting the result.
🧪 Practical tip:
If an abnormal NLR value is detected, it is worthwhile to also check other inflammatory parameters such as... Fibrinogen, CRP (if available), temperature, general behavior and other hematological findings to be included in the clinical assessment.
📊 Decision tree: NLR determination in cats
< 3.0 = normal
3.0 – 5.0 = slightly increased
5.1 – 10.0 = moderately increased
10.1 – 20.0 = significantly increased
> 20.0 = greatly increased
🔹 Search for source of inflammation / trauma
🔹 Consider intensive monitoring
🔹 Initiate further diagnostic procedures (e.g., X-ray, CRP, ultrasound)
🔹 Plan progress monitoring
✅ What this graphic offers:
- Clear decision tree: Guides you through the most important questions and actions.
- Practical: Ideal for veterinarians to communicate within their team or with pet owners.
Here are 5 Frequently Asked Questions (FAQ) all about the topic Neutrophil-to-lymphocyte ratio (NLR) in cats
What exactly does the neutrophil-to-lymphocyte ratio (NLR) tell us about my cat's health?
The Neutrophil-to-lymphocyte ratio (NLR) is an indirect marker for the state of your cat's immune system. It describes the ratio between two important cell types in the blood: the Neutrophils, which primarily react to acute inflammation and tissue damage, and the Lymphocytes, which are more responsible for targeted, adaptive immune defense – for example in viral infections or long-term immune responses.
A elevated NLR value This usually means that your cat's body is in a state of readiness. acute stress or inflammation reacts – be it due to trauma, infection, stress, or another systemic illness. At the same time, a drop in lymphocytes can be an indication of a Weakening of the specific immune system This can occur, as is the case with heavy physical exertion, chronic stress, or immunomodulatory diseases.
A low or normal NLR value Conversely, a negative NLR usually indicates that the immune system is functioning in a healthy balance. This makes the NLR a valuable tool in assessing a cat's overall health – especially in emergency or intensive care medicine.
When should my cat's NLR be tested? Are there any typical situations or symptoms?
Determining the NLR is particularly useful when There is a suspicion of an acute or systemic illness or if your cat has recently blunt trauma (e.g., fall, accident). Also in cases where your cat suddenly appears apathetic, has a fever, doesn't eat or breathes heavily, The NLR can help to better narrow down the causes.
Typical situations for determining NLR include:
After Falls or accidents, in which internal injuries cannot be ruled out
With unexplained signs of inflammation or suspected infection (e.g., fever of unknown origin)
With chronic diseases, e.g., cancer, inflammatory bowel diseases, or autoimmune processes
To Therapy control, to see how the body reacts to medications or treatments
With intensive care patients, in order to monitor the course of the disease
The NLR can therefore be a valuable component of diagnostics – however, it never replaces clinical examination or other laboratory and imaging procedures. It helps to..., Early warning signs should be taken seriously and to initiate further diagnostic steps in a more targeted manner.
What could be the causes of an elevated NLR level in my cat?
An elevated NLR level in a cat can have a variety of causes. Generally, a high NLR indicates that there is a problem in the body. increased inflammatory or stress response The following causes are possible in detail:
Acute traumae.g. after a fall from a great height (high-rise syndrome), a traffic accident or a fight
Infections: bacterial infections (e.g., abscesses, pneumonia), viral diseases with a secondary bacterial component
Stress reactionsTransport, vet visits, severe pain – all of these can temporarily increase the NLR.
Chronic inflammatione.g., in cases of chronic enteritis, pancreatitis, or immune-mediated diseases
Neoplasms (Cancer): Some tumors lead to a systemic inflammatory response that increases the NLR.
Medications or hormonal disordersCortisone treatments or thyroid problems can affect the ratio.
Sepsis or multiple organ failureIn very severe cases, an extremely high NLR can also indicate a systemic derailment.
It is important that a single high NLR value No diagnosis concluded is, but a signal, that a closer look should be taken – possibly through further examinations such as X-rays, ultrasound, CRP determination or fibrinogen measurement.
Are there normal values for the NLR in cats? And when should one start to worry?
There are no rigid, internationally valid normative values for the NLR in cats, as the value can vary depending on age, health status, stress level, and examination method. However, studies with healthy cats show that the The normal range is approximately an NLR of 2.0 to 3.0..
Based on clinical experience and current research data (e.g. Doulidis et al., 2024The following areas of orientation can be derived:
NLR value
assessment
Below 3.0
Normal range
3.0 – 5.0
Slightly elevated – observation recommended
5.1 – 10.0
Moderately elevated – possible inflammation
10.1 – 20.0
Significantly elevated – further investigation is needed.
Over 20.0
Significantly increased – potential emergency
A value over 4.45 was already described in the aforementioned study as significantly increased limit value This value is recognized in cats with trauma. If such a value is measured, a follow-up examination should always be performed. physical cause sought and, if necessary, close monitoring may be initiated.
Can the NLR also be used for monitoring the progress of sick cats?
Yes, the NLR is ideally suited for the Progress monitoring – especially in cats being treated for trauma, infection, or chronic illnesses. Monitoring the NLR over several days or weeks can help to determine the Effect of a therapy to assess or to detect complications early.
For example: A cat with severe thoracic trauma initially has an NLR of 15. After 3 days of intensive therapy, the value drops to 7, and after one week to 3.5. This suggests a positive development and reduction of inflammatory activity. However, if the NLR remains high or rises again, this could indicate Complications such as infections, pleural effusion, or stress due to pain point out.
Important: The NLR curve should not isolated be considered, but always in relation to clinical symptoms, vital signs and other laboratory values (e.g., temperature, eating habits, CRP, fibrinogen, liver values, etc.). Nevertheless, it can be a very practical and quick early warning system – especially for cats requiring intensive care or those at high risk.
Summary of neutrophil-to-lymphocyte ratio in cats
The Neutrophil-to-lymphocyte ratio in cats It is increasingly developing into a valuable diagnostic and prognostic marker in small animal medicine. While it has been used successfully in human medicine for years to assess inflammatory processes, stress reactions, and disease progression, it is also becoming increasingly important in the field. Neutrophil-to-lymphocyte ratio in cats increasingly becoming the focus of research and clinical application.
The Neutrophil-to-lymphocyte ratio in cats It is based on the determination of two important cell types in the blood count: neutrophils and lymphocytes. In healthy animals, the Neutrophil-to-lymphocyte ratio in cats in the range of approximately 2 to 3. If this ratio increases, it indicates a predominance of the non-specific immune response, such as occurs with infections, trauma, or systemic stress. Thus, an increased Neutrophil-to-lymphocyte ratio in cats It can be an early warning sign of inflammatory or critical processes in the body.
This is particularly evident after blunt trauma – such as after a fall, a car accident or other injuries. Neutrophil-to-lymphocyte ratio in cats a clear correlation with the severity of the clinical picture. In a retrospective study of 177 cats, it was found that the Neutrophil-to-lymphocyte ratio in cats The risk was significantly higher in severely injured animals than in slightly injured or healthy animals.
A specific limit of 4.45 for the Neutrophil-to-lymphocyte ratio in cats It was able to differentiate between healthy and injured animals with good sensitivity and specificity. This was particularly noticeable in cases of thoracic trauma. Neutrophil-to-lymphocyte ratio in cats significantly. Therefore, it is recommended that the Neutrophil-to-lymphocyte ratio in cats not only for initial assessment, but also for monitoring the progress of patients with internal medicine or traumatological problems.
Furthermore, the Neutrophil-to-lymphocyte ratio in cats They provide important guidance on managing chronic inflammation, immune-mediated diseases, and even tumors. Studies show that this Neutrophil-to-lymphocyte ratio in cats in neoplasms it is often significantly elevated – a sign that tumor-associated inflammation also plays a role.
It is therefore helpful for veterinarians to know that Neutrophil-to-lymphocyte ratio in cats to anchor it in the diagnostic toolbox. Since it is calculated based on a simple blood test, it is Neutrophil-to-lymphocyte ratio in cats Cost-effective and quickly available – without additional lab costs or waiting times. However, it is important to note that manual differentiation is recommended for abnormal results to avoid misinterpretations caused by machine counting. This is the only way to ensure... Neutrophil-to-lymphocyte ratio in cats be evaluated in a truly reliable manner.
In emergency medicine, this provides Neutrophil-to-lymphocyte ratio in cats Furthermore, it provides rapid indications of which animals potentially require intensive care. It can also aid in assessing the prognosis. Neutrophil-to-lymphocyte ratio in cats be important – especially in combination with other parameters such as the Animal Trauma Triage (ATT) score or inflammatory markers such as fibrinogen or CRP.
A decisive advantage: The Neutrophil-to-lymphocyte ratio in cats This can be tracked over time. In hospitalized patients, repeated blood tests can reveal whether the ratio improves or worsens – and thus allow conclusions to be drawn about the course of therapy. If the Neutrophil-to-lymphocyte ratio in cats If it decreases, this may indicate successful treatment; if it remains high or continues to rise, special vigilance is required.
Pet owners also benefit from a simple explanation of the Neutrophil-to-lymphocyte ratio in cats, as it helps to make the need for diagnostics or inpatient monitoring more understandable. This can be particularly helpful in communication surrounding seriously ill animals. Neutrophil-to-lymphocyte ratio in cats to help make informed decisions.
In summary, it can be said that: Neutrophil-to-lymphocyte ratio in cats It is a straightforward yet highly informative marker of health status. It can provide valuable services in acute and chronic illnesses, in emergency care, and in monitoring disease progression. Its increasing clinical and scientific relevance demonstrates that it Neutrophil-to-lymphocyte ratio in cats has found its firm place in modern veterinary medicine – and will gain even more importance in the future.
Further sources:
- Ay CD. Neutrophil to lymphocyte ratio as a prognostic biomarker in puppies with acute diarrhea. J Vet Emerg Crit Care (San Antonio). 2022;32(1):83-89. doi:10.1111/vec.13159
- Conway EA, Del Valle CP, Waugh EM, French A, Ridyard AE. Retrospective investigation of the neutrophil-to-lymphocyte ratio in dogs with pneumonia: 49 cases (2011-2016). J Vet Emerg Crit Care (San Antonio). 2021;31(4):490-497. doi:10.1111/vec.13067
- Johnson MM, Gicking JC, Keys DA. Evaluation of red blood cell distribution width, neutrophil-to-lymphocyte ratio, and other hematologic parameters in canine acute pancreatitis. J Vet Emerg Crit Care (San Antonio). 2023;33(5):587-597. doi:10.1111/vec.13325
- Dourmashkin LH, Lyons B, Hess RS, Walsh K, Silverstein DC. Evaluation of the neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios in critically ill dogs. J Vet Emerg Crit Care (San Antonio). 2023;33(1):52-58. doi:10.1111/vec.13269