What is a hematocrit test. How is it performed. Why might your hematocrit be high. What are the normal ranges for hematocrit. When should you be concerned about high hematocrit levels.

What is Hematocrit and Why is it Important?

Hematocrit is a crucial blood test that measures the percentage of red blood cells in your total blood volume. This test provides valuable insights into your overall health and can indicate various medical conditions. Understanding hematocrit is essential for both patients and healthcare providers.

Red blood cells play a vital role in your body’s functions. They are responsible for:

• Transporting oxygen to body tissues
• Carrying nutrients throughout the body
• Removing waste products and carbon dioxide
• Distributing hormones from endocrine organs to target tissues
• Maintaining body temperature
• Regulating pH levels in body tissues
• Assisting in clot formation and infection prevention

Given these critical functions, monitoring your hematocrit levels can provide valuable information about your overall health status.

The Hematocrit Test Procedure: What to Expect

The hematocrit test is a simple and routine procedure that requires a blood sample. Here’s what you can expect during the test:

1. A healthcare professional will clean the area where the blood will be drawn, usually from a vein in your arm.
2. They will insert a small needle into the vein to collect the blood sample.
3. You may feel a slight prick or stinging sensation when the needle is inserted.
4. The blood sample is collected in a vial or tube.
5. After the sample is taken, the needle is removed, and pressure is applied to stop any bleeding.
6. The entire process typically takes just a few minutes.

Most people experience minimal discomfort during the procedure. Some may feel a throbbing sensation or have a slight bruise afterward, but these effects usually subside quickly.

Is any special preparation required for a hematocrit test?

No special preparation is necessary for a hematocrit test. You can eat and drink normally before the test unless your healthcare provider instructs otherwise. If you’re taking any medications, inform your doctor, as some drugs may affect the test results.

Interpreting Hematocrit Test Results: Normal Ranges

Understanding your hematocrit test results is crucial for assessing your health status. Normal hematocrit ranges vary depending on age and gender:

• Adult males: 40.7% to 50.3%
• Adult females: 36.1% to 44.3%
• Newborns: 45% to 61%
• Infants: 32% to 42%

It’s important to note that these ranges can vary slightly between laboratories. Always consult with your healthcare provider to interpret your specific test results accurately.

Can hematocrit levels fluctuate naturally?

Yes, hematocrit levels can fluctuate due to various factors such as altitude, hydration status, and recent physical activity. For instance, people living at high altitudes tend to have higher hematocrit levels as their bodies produce more red blood cells to compensate for lower oxygen levels in the air.

High Hematocrit: Causes and Implications

A high hematocrit level, also known as polycythemia, occurs when the percentage of red blood cells in your blood is above the normal range. Several factors can contribute to elevated hematocrit levels:

• Dehydration: When you’re dehydrated, the concentration of red blood cells in your blood increases.
• Smoking: Tobacco use can lead to increased red blood cell production.
• Lung diseases: Conditions like chronic obstructive pulmonary disease (COPD) can cause the body to produce more red blood cells to compensate for low oxygen levels.
• Heart diseases: Certain heart conditions may result in increased red blood cell production.
• Polycythemia vera: This rare blood disorder causes your bone marrow to produce too many red blood cells.
• Living at high altitudes: Your body naturally produces more red blood cells to adapt to lower oxygen levels at higher elevations.
• Certain medications: Some drugs, such as anabolic steroids or erythropoietin, can stimulate red blood cell production.

What are the potential consequences of persistently high hematocrit levels?

Chronically elevated hematocrit levels can lead to various health complications, including:

• Increased risk of blood clots, which may result in stroke or heart attack
• Impaired blood flow due to increased blood viscosity
• Headaches and dizziness
• Vision problems
• Itching, especially after exposure to warm water
• Fatigue and weakness

If you consistently have high hematocrit levels, your healthcare provider will work to identify and address the underlying cause to prevent these potential complications.

When to Seek Medical Attention for High Hematocrit

While a single high hematocrit reading may not always be cause for alarm, certain situations warrant medical attention:

• Persistent high readings on multiple tests
• Symptoms such as severe headaches, vision changes, or shortness of breath
• A family history of blood disorders
• Recent travel to high-altitude locations
• Unexplained weight loss or night sweats
• History of blood clots or cardiovascular disease

Your healthcare provider may recommend additional tests or refer you to a hematologist for further evaluation if they suspect an underlying condition causing your high hematocrit levels.

How often should hematocrit levels be monitored?

The frequency of hematocrit testing depends on various factors, including your overall health, age, and any pre-existing medical conditions. For healthy individuals, hematocrit levels are typically checked as part of routine annual physical exams. However, if you have a history of blood disorders or other relevant health issues, your doctor may recommend more frequent testing.

Managing High Hematocrit: Treatment Options and Lifestyle Changes

If you’ve been diagnosed with high hematocrit levels, your healthcare provider may recommend various treatment options depending on the underlying cause:

1. Phlebotomy: This procedure involves removing blood to reduce the number of red blood cells. It’s often used for conditions like polycythemia vera.
2. Hydration: Increasing your fluid intake can help dilute your blood and lower hematocrit levels, especially if dehydration is the cause.
3. Medication adjustments: If certain medications are causing high hematocrit, your doctor may adjust your dosage or switch to alternative treatments.
4. Treating underlying conditions: Addressing any underlying health issues, such as lung or heart diseases, can help normalize hematocrit levels.
5. Lifestyle changes: Quitting smoking, maintaining a healthy weight, and regular exercise can positively impact your hematocrit levels.

Are there any dietary changes that can help manage high hematocrit?

While diet alone may not significantly lower high hematocrit levels caused by medical conditions, certain dietary changes can support overall blood health:

• Stay hydrated by drinking plenty of water throughout the day
• Limit alcohol consumption, as it can contribute to dehydration
• Reduce salt intake to help manage blood pressure
• Incorporate foods rich in antioxidants, such as fruits and vegetables, to support overall cardiovascular health
• Consider reducing iron-rich foods if your doctor recommends it, especially if you have hemochromatosis

Always consult with your healthcare provider before making significant changes to your diet, especially if you have underlying health conditions.

Hematocrit and Other Blood Tests: Understanding the Big Picture

Hematocrit is typically part of a complete blood count (CBC), which provides a comprehensive overview of your blood health. Other components of a CBC include:

• Red blood cell count (RBC)
• White blood cell count (WBC)
• Hemoglobin levels
• Platelet count
• Mean corpuscular volume (MCV)
• Mean corpuscular hemoglobin (MCH)
• Mean corpuscular hemoglobin concentration (MCHC)

These tests, when interpreted together, provide a more comprehensive understanding of your blood health and can help identify various blood disorders or other health issues.

How do hematocrit levels relate to hemoglobin levels?

Hematocrit and hemoglobin levels are closely related. Hemoglobin is the protein in red blood cells responsible for carrying oxygen. Generally, hematocrit levels are about three times the hemoglobin level. For example, if your hemoglobin is 15 g/dL, your hematocrit would be expected to be around 45%. However, this relationship can vary in certain medical conditions, which is why both tests are typically performed together.

Special Considerations: Hematocrit in Pregnancy and Athletes

Certain populations may have unique considerations when it comes to hematocrit levels:

Pregnancy and Hematocrit

During pregnancy, a woman’s blood volume increases significantly, which can lead to a relative decrease in hematocrit levels. This is a normal physiological change and doesn’t typically require treatment. However, healthcare providers closely monitor hematocrit levels throughout pregnancy to ensure they don’t drop too low, which could indicate anemia.

Athletes and Hematocrit

Endurance athletes, particularly those training at high altitudes, may naturally have higher hematocrit levels due to their bodies’ adaptation to increased oxygen demands. However, abnormally high levels in athletes can also be a sign of blood doping, a banned practice in competitive sports where athletes artificially increase their red blood cell count to enhance performance.

Regular monitoring of hematocrit levels is crucial for these groups to ensure optimal health and, in the case of athletes, compliance with sports regulations.

Can lifestyle factors influence hematocrit levels in healthy individuals?

Yes, several lifestyle factors can affect hematocrit levels even in otherwise healthy individuals:

• Hydration status: Dehydration can temporarily increase hematocrit levels
• Altitude: Living or training at high altitudes can lead to increased red blood cell production
• Exercise: Regular intense physical activity can slightly increase hematocrit levels
• Smoking: Tobacco use can elevate hematocrit levels
• Stress: Chronic stress may impact hematocrit levels through various physiological mechanisms

Understanding these factors can help individuals and healthcare providers better interpret hematocrit test results in the context of overall health and lifestyle.

Hematocrit Information | Mount Sinai

HCT

Hematocrit is a blood test that measures how much of a person’s blood is made up of red blood cells. This measurement depends on the number of and size of the red blood cells.

Blood transports oxygen and nutrients to body tissues and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For example, blood transports hormones from endocrine organs to their target organs and tissues. Blood helps maintain body temperature and normal pH levels in body tissues. The protective functions of blood include clot formation and the prevention of infection.

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

No special preparation is necessary for this test.

How the Test will Feel

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.

Why the Test is Performed

The hematocrit is almost always done as part of a complete blood count (CBC).

Your health care provider may recommend this test if you have signs of or are at risk for anemia. These include having:

• Before and after major surgery
• Blood in your stools, or vomit (if you throw up)
• Chronic medical problems, such as kidney disease or certain types of arthritis
• During pregnancy
• Fatigue, poor health, or unexplained weight loss
• Headaches
• Heavy menstrual periods
• Leukemia or other problems in the bone marrow
• Monitoring during treatment for cancer
• Monitoring medicines that may cause anemia or low blood counts
• Monitoring of anemia and its cause
• Poor nutrition
• Problems concentrating

Normal Results

Normal results vary, but in general they are:

• Male: 40. 7% to 50.3%
• Female: 36.1% to 44.3%

For babies, normal results are:

• Newborn: 45% to 61%
• Infant: 32% to 42%

The examples above are common measurements for results of these tests. Normal value ranges vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

Low hematocrit may be due to:

• Anemia
• Bleeding

• Bone marrow being unable to produce new red blood cells. This may be due to leukemia, other cancers, drug toxicity, radiation therapy, infection, or bone marrow disorders 

• Chronic illness
• Chronic kidney disease
• Destruction of red blood cells (hemolysis)
• Leukemia
• Malnutrition
• Too little iron, folate, vitamin B12, and vitamin B6 in the diet
• Too much water in the body

High hematocrit may be due to:

• Bone marrow disease that causes abnormal increase in red blood cells (polycythemia vera)
• Congenital heart disease
• Exposure to high altitude
• Failure of the right side of the heart
• Low levels of oxygen in the blood
• Scarring or thickening of the lungs
• Too little water in the body (dehydration)

Risks

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Other risks associated with having blood drawn are slight but may include:

• Excessive bleeding
• Fainting or feeling lightheaded
• Multiple punctures to locate veins
• Hematoma (blood buildup under the skin)
• Infection (a slight risk any time the skin is broken)

Chernecky CC, Berger BJ. H. Hematocrit blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:620-621.

Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM. Blood disorders. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 124.

Means RT. Approach to the anemias. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 149.

Vajpayee N, Graham SS, Bem S. Basic examination of blood and bone marrow. In: McPherson RA, Pincus MR, eds. Henry’s Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 31.

Last reviewed on: 1/9/2022

Reviewed by: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

What It Means to Get High or Low Results > Personalabs

The hematocrit or HCT blood test measures the proportion of red blood cells to white blood cells, platelets, and plasma.  

High HCT blood test values (usually over 44% to 50%) indicate dehydration and conditions that cause RBC overproduction. Alternatively, extremely low hematocrit results may indicate anemia or other blood disorders that affect RBC formation (erythropoiesis) or destruction (hemolysis). 

Know more about the concerning levels of HCT and what the test results tell you when you read on.

Pro Tip: Hematocrit and other parts of the complete blood count (CBC) reveal essential information about your health. If you wish to learn more about what your blood test means, book a virtual consultation to speak to a healthcare provider. 

High HCT Meaning 

If your HCT blood test result shows high hematocrit, over 50% for men and 44% for women, it suggests that you have more red blood cells or erythrocytes due to an underlying health condition. It could also indicate that blood plasma is in critically low volume. 

Symptoms of high hematocrit include:

• Fatigue
• Dizziness 
• Headaches
• Vision problems
• Skin blushing or flushing

Causes of High HCT

Dehydration

If you have high HCT, you are likely to be dehydrated. In this case, you may not necessarily be producing too many RBCs. Instead, your blood has a low volume of plasma which stems from a lack of proper hydration. 

Lung Disease

Conditions affecting lung function, such as chronic obstructive pulmonary disease (COPD), can affect the organ’s ability to obtain oxygen. To compensate for the oxygen shortage, your body will produce more RBCs. If you have symptoms of pulmonary disorders, your doctor may order additional laboratory tests, including lung function blood tests. 

Heart Disease

People with heart disease are prone to high hematocrit and hemoglobin. As the heart cannot function fully to facilitate blood circulation, your body will counteract the said loss with increased erythrocyte production. Thus, an HCT blood test also provides additional information about your risk for cardiovascular diseases, making it a key part of heart health blood tests. 

Cancer

The primary cancer type that drives your bone marrow to produce excessive red blood cells is called polycythemia vera. Although extremely rare, this blood cancer slows down blood circulation, and leads to an enlarged spleen, increased blood clotting, and other life-threatening blood-related complications. Naturally, it also elevates your normal hematocrit levels. 

On the other hand, kidney cancer also influences erythrocyte production since it releases the protein (erythropoietin) that prompts the process. This can be further confirmed by additional tests, such as a red blood cell count, biopsy, MRI, etc. 

Did You Know? Several cancers can be detected by biomarkers screened through a blood test. In some cases, these cancers are first spotted through routine exams. Learn more about the types of cancer diagnosed through blood testing. 

Treatment for Elevated HCT

Lowering your high HCT will depend on its cause. For example, if it’s due to dehydration, your healthcare provider may recommend rehydration therapy. If your test result goes extremely above the normal range for HCT, your doctor may push for phlebotomy, wherein blood is extracted to reduce red blood cell count.  

Low HCT Meaning 

To get an HCT below the normal hematocrit range (less than 41% for men and 36% for women) indicates low red blood production or a high rate of destruction, potentially due to an underlying illness. 

The most common cause of low hematocrit is anemia, characterized by a reduced number of healthy red blood cells. You may spot anemia through the following symptoms:

• Fatigue
• Dizziness 
• Chest pain
• Headaches 
• Pale complexion
• Trouble breathing
• Cold hands and feet
• Irregular heartbeat (arrhythmia) 

Causes of Low HCT

Anemias 

As mentioned above, low HCT typically signals anemia, which can be due to a lack of nutrients, such as that in iron-deficiency anemia, or genetic factors like what’s causing sickle cell anemia and aplastic anemia. Additional blood tests are needed to verify the condition, including the anemia profile blood test. 

Blood Loss

Women who experience excessive menstrual bleeding are likely to have low HCT. In the same way, those who suffer from bacterial ulcers caused by H. pylori and other similar disorders leading to internal bleeding can also expect decreased HCT in their blood test. 

Did You Know? It’s possible to experience blood loss without seeing blood in your stool, as the naked eye does not easily detect it. Get the fecal occult blood test to determine if you have chronic digestive bleeding.

Thalassemia 

Thalassemia is an inherited blood disorder wherein your body fails to produce enough hemoglobin, a crucial protein in the red blood cell. As a result, RBCs are low, indicated by low HCT and erythrocyte count.  

Kidney Problems

Your kidneys don’t just filter wastes from the blood. They also produce the protein erythropoietin, which signals the production of RBCs. Hence, disorders like chronic kidney disease (CKD) and other significant kidney problems lead to low secretion of erythropoietin, resulting in inadequate RBCs.  

Inflammatory Diseases

Conditions like lupus and rheumatoid arthritis, characterized by increased inflammatory activities, negatively influence RBC formation and maturation. Similarly, inflammatory bowel disease (IBD) may also promote anemia leading to low HCT as it affects the absorption of iron, copper, vitamin B12, and other fundamental nutrients for erythropoiesis.  

Cancers

Leukemia and lymphoma are two types of cancers that directly impact bone marrow function. Hence, with these underlying conditions, you may likely get low HCT in your blood test and undergo further testing. 

Treatment for Low HCT

If low HCT is due to iron-deficiency anemia, your doctor may recommend supplements and certain lifestyle adjustments. Learn more about iron deficiency anemia and its physical impact, especially among women. 

On the other hand, if the condition is linked to more complex disorders like cancer, blood disease, CKD, etc., your healthcare provider will need more information to form an accurate diagnosis, entailing other types of assessment. Only then will your doctor prescribe a treatment that covers the process in which HCT is brought to its normal range.

How Is Hematocrit Measured?

Calculating hematocrit involves measuring the ratio of red blood cells through a reading device. When using a capillary tube, the length of the RBC packed length volume is compared to the total length of the blood sample. 

It is imperative to have the analysis within 10 minutes of the sample collection, as the erythrocyte layers can mix with the other blood components and platelets begin to clot. 

How and When Is It Done?

Your doctor will likely order an HCT blood test if you exhibit symptoms of anemia, blood loss, dehydration, and other blood disorders. As part of the CBC test, it also provides critical information on other disorders, such as cancer, lung disease, kidney disease, liver problems, and cardiovascular diseases. 

Unlike the other tests involved in CBC, wherein the blood samples can be collected through finger pricking, an HCT blood test will require a venous blood sample. This is drawn from the veins at the back of your elbow and should only be performed by a licensed phlebotomist. HCT measurement needs more volume of blood for accurate processing and analysis. 

Additionally, an HCT blood test alone does not require fasting or other special preparations prior to blood collection. But if it is part of a more extensive test or if you’re taking another test simultaneously, you may have to abstain from consuming food, drinks, and certain medications. 

Pro Tip: Venipuncture, the process of inserting a syringe needle into your vein for blood collection, can be a little discomforting. If you are anxious about your lab test appointment, read our tips on how to calm yourself when getting blood drawn. 

Frequently Asked Questions

What level of HCT is concerning?

The normal hematocrit range for men is 41% to 50%, while women should have 36% to 44%. HCT test values that go above or below these ranges signal problems in the blood ranging from anemia to blood loss for low HCT percentage and dehydration to blood cancer for high lab values. Either way, see your doctor for a proper diagnosis and additional lab tests. 

Can high HCT cause fatigue?

Feeling exhausted all the time is part of the symptoms of high HCT. The increased volume of RBCs causes the blood to be thicker and move slower, affecting the rate of oxygen distribution to cells. As a result, your brain receives less oxygen, making you tired and sleepy. 

Does low HCT mean dehydration?

It’s the other way around. Low HCT suggests conditions like anemia and other blood disorders, but it’s high HCT that indicates dehydration. The lack of sufficient fluid in your body results in blood plasma having less volume, which increases the percentage of RBC. 

Did You Know? Aside from an HCT blood test, other ways to detect dehydration include a urinalysis and the electrolyte blood test panel. Treatment for severe dehydration includes administering IV fluids and oral rehydration solution (ORS).  

The Bottom Line 

An HCT blood test helps detect various health conditions, especially blood disorders. However, without fully understanding what your test results mean may lead to misconceptions about the severity of the abnormality. In addition, it’s important to understand that a hematocrit blood test alone will not suffice as far as diagnosis goes. It’s always the best course of action to speak to your doctor whether by setting up an appointment, either for a physical or virtual consultation.

Hematocrit

Hematocrit is the ratio of the volume of erythrocytes to the volume of the liquid part of the blood.

Determination of hematocrit is an integral part of the general blood test and is not performed separately.

Russian synonyms

Hematocrit value.

Synonyms English

Ht, Hct, Hematocrit, Crit, Haematocrit, PCV, Packed Cell Volume.

Units

% (percentage).

What biomaterial can be used for research?

Venous or capillary blood.

General information about the study

Hematocrit measures the volume of blood that red blood cells occupy in the bloodstream. This indicator is expressed as a percentage. For example, a hematocrit of 45% means that 100 milliliters of blood contains 45 milliliters of red blood cells.

An increase in hematocrit occurs if the number of red blood cells increases or the volume of the liquid part of the blood decreases, which happens when the body loses excess fluid (for example, with diarrhea). A decrease in this indicator is observed, on the contrary, with a decrease in the number of red blood cells (for example, due to their loss, destruction, or a decrease in their formation) or with overhydration – when a person receives too much fluid (for example, with excessive administration of intravenous solutions).

Hematocrit reflects not only the number of red blood cells, but also their size. If the size of red blood cells decreases (as in iron deficiency anemia), the hematocrit will also decrease.

What is research used for?

• In the diagnosis of anemia and polycythemia and to evaluate the effectiveness of their treatment.
• To determine the degree of dehydration.
• As one of the criteria for deciding on the need for a blood transfusion.
• To evaluate the effectiveness of blood transfusions.

When is the test ordered?

This test is part of a routine complete blood count, which is performed both routinely and in various diseases and pathological conditions, before surgical interventions.

In addition, it can be carried out repeatedly and at certain intervals:

• for dynamic monitoring and evaluation of the effectiveness of the treatment of anemia and polycythemia,
• after conditions causing dehydration,
• for recurrent bleeding for a comprehensive assessment of their severity.

What do the results mean?

Reference values ​​

Generally, the hematocrit corresponds to the number of red blood cells, but this is only true when the size of the red blood cells is normal. If the number of normal-sized red blood cells increases, the hematocrit also rises. In cases of large or small erythrocytes, this is not always the case. For example, with iron deficiency, red blood cells decrease and the hematocrit will be reduced, but the number of red blood cells per unit of blood may be normal and even slightly higher.

Hematocrit level above 55% requires clarification of the cause and further diagnostic search.

Causes of low hematocrit:

• iron-, B ₁₂ – or folic deficiency anemia,
• acute or chronic bleeding (during or immediately after bleeding, hematocrit and hemoglobin will be elevated),
• disorders of hemoglobin synthesis (sickle cell anemia, thalassemia),
• cirrhosis of the liver,
• destruction of red blood cells as a result of hemolysis – the destruction of red blood cells inside the body (it can occur for various reasons – due to a hereditary defect in red blood cells, as a result of the appearance of antibodies to one’s own red blood cells or toxic effects in malaria),
• oncological diseases of the bone marrow or metastases of other tumors in the bone marrow, leading to a decrease in the synthesis of red blood cells,
• excessive hydration of the body – the introduction of large volumes of intravenous fluids.

Causes of increased hematocrit:

• dehydration (dehydration) of any origin – due to diarrhea, profuse vomiting, diabetes, after burns,
• polycythemia vera due to excessive production of red blood cells in the bone marrow,
• chronic obstructive pulmonary disease,
• chronic heart failure.

What can influence the result of ?

1. The hematocrit level is normally reduced in pregnant women due to a physiological increase in the volume of the liquid part of the blood.
2. Persons ascending to high altitudes experience an increase in the number of red blood cells and, consequently, hematocrit, as their body adapts to the reduced oxygen concentration.
3. Hematocrit may be increased in smokers due to oxygen deprivation of tissues and increased production of red blood cells.
4. In newborns, the hematocrit level is increased, since they have quite a lot of large red blood cells in their blood.

Important Notes

• Red blood cell count, hemoglobin and hematocrit are strongly related to the degree of body hydration. If the volume of the liquid part of the blood decreases with excessive fluid loss, these indicators will increase. However, the absolute number of erythrocytes and hemoglobin does not change.

Also recommended

• Clinical blood test: complete analysis, leukocyte count, ESR (with blood smear microscopy if pathological changes are detected)
• Erythrocyte indices
• Reticulocytes
• Erythropoietin
• Erythrocytes
• Hemoglobin

Who orders the examination?

General practitioner, internist, hematologist, nephrologist, surgeon.

Hematocrit targets for therapeutic bloodletting in patients with polycythemia vera

PUBLICATIONS

Polycythemia vera (polycythemia vera) is a myeloproliferative disease in which there is an increased production of red blood cells, granulocytes and platelets. The development of the disease is associated with a mutation (V617F) in the tyrosine kinase 9 gene0377 JAK2 . However, the JAK2V617F mutation is also found in half of patients with essential thrombocytosis, primary myelofibrosis, which reduces the specificity of detecting this genetic breakdown in the diagnosis of polycythemia vera.

There is no doubt that erythrocytosis plays a negative role in the development of blood stasis, platelet activation and hypercoagulability, endothelial damage (“Virchow’s triad”), however, the place of bloodletting in the treatment of polycythemia vera remains controversial.

The Polycythemia Vera Study Group (PVSG) compared the efficacy of bloodletting and treatment with radioactive phosphorus or chemotherapeutic agents. In the group of patients treated with bloodletting, there was a higher incidence of thrombotic complications, but in the other two groups there was an increased incidence of acute leukemia. It should be noted that the target hematocrit values ​​in this study were ≤ 52%.

The main reason for opposition to bloodletting as a treatment is the difficulty in objectively assessing the total blood volume that increases in polycythemia (especially splenomegaly). The increase in plasma volume contributes to the “pseudonormalization” of hematocrit, and in some cases may make it difficult to recognize polycythemia according to the criteria of the World Health Organization; in such cases, it is reasonable to exclude the JAK2V617F mutation.

If in vitro we estimate hematocrit as the proportion of red blood cells in the blood volume, then in vivo the distribution of plasma and red blood cells in the bloodstream may vary depending on the type of vessels and the patient’s condition (the presence of dehydration, tissue hypoxia). Hematocrit in vivo may differ significantly from values ​​obtained in the laboratory. The hematocrit measured in the analysis of peripheral blood, as a rule, is less than that observed in large vessels.

Marchioli R. et al. evaluated the effect of therapeutic bloodletting, hydroxyurea therapy or both in the general group of patients with polycythemia vera (n=365). Mortality from cardiovascular complications and thrombosis were compared when the target level of hematocrit was reached.

Figure 1. Kaplan-Meier curves for the primary endpoint of assessing the risk of death from cardiovascular complications or thrombosis in the Marchioli R. et al.

There were no significant differences in other outcomes.

Thus, when performing therapeutic bloodletting in patients with polycythemia vera, the target hematocrit values ​​should be

Acetylsalicylic acid and hydroxyurea preparations are currently recommended for the prevention of arterial and venous thrombosis in polycythemia. But, as Marchioli R. et al. showed in their work, maintaining hematocrit is of the greatest importance for reducing the risk of thrombosis.

Source: Marchioli R.