Every second, the human body produces an impressive 17 million new red blood cells (RBCs), also known as erythrocytes. These vital cells transport oxygen and nutrients throughout the body.
A red blood cell count measures the number of RBCs in the blood, an essential routine test for assessing overall health. Abnormal RBC counts, whether high or low, can indicate underlying health issues that warrant further investigation.
Understanding high RBC counts is essential for practitioners and patients, as it can provide insights into various medical conditions and inform treatment decisions. This article offers a comprehensive guide on high RBC counts, emphasizing their significance in clinical practice and patient care.
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What Does High RBC Count Mean?
A high RBC count, also known as erythrocytosis or polycythemia, is when the number of red blood cells in the bloodstream is higher than normal.
Although normal ranges can vary between laboratories, adults typically have RBC counts ranging from 4.2 to 5.9 million cells per microliter (μL) of blood. These ranges also vary by sex:
- Adult males: 4.5-5.9 million cells/μL
- Adult females: 4.0-5.2 million cells/μL
Normal RBC counts for children generally fall between 4.0 and 5.5 million cells/μL, depending on age and sex. The RBC count is measured as part of a Complete Blood Count (CBC), a routine blood test ordered by healthcare providers to monitor and screen for various health conditions.
What Happens if RBC Count is High?
An elevated RBC count can impact the body in several ways, influenced by the root cause and the extent of the elevation.
Symptoms
While those with high RBC counts may be asymptomatic, commonly associated symptoms include:
More severe cases may be associated with:
- High blood pressure
- Unexplained weight loss
- Joint pain, swelling, and tenderness
- Numbness or tingling in the extremities
- Itchy skin, especially after bathing in warm water
- Nosebleeds or easy bruising
Potential Complications
While some effects may be mild, more severe cases can lead to hyperviscosity (thickening) of the blood, increasing the risk of sluggish blood flow, blood clots, and life-threatening outcomes, including:
- Stroke
- Heart attack
- Pulmonary embolism (PE): A blockage in the blood vessel that carries blood from the heart to the lungs
- Deep vein thrombosis (DVT): A blockage in the deep vessels (typically of the leg) that can travel to the lungs and cause a PE
What Causes High RBC Count?
Identifying the cause of a high RBC count is crucial for effective management. These causes can generally be classified into primary and secondary categories.
Primary Causes
Primary erythrocytosis originates from a problem in the bone marrow, the spongy tissue inside the bones that produce RBCs. It is often due to a genetic defect that causes increased production of stem cells, which mature into RBCs. Primary erythrocytosis can be inherited (present at birth) or acquired (developed over time).
Polycythemia vera (PV) is the most common type of acquired primary erythrocytosis. Elevated levels of RBCs mark this rare blood cancer, which often involves increases in white blood cells (WBCs) and platelets as well.
Secondary Causes
Secondary erythrocytosis results from problems originating outside of the bone marrow. Most commonly, it is caused by the overproduction of erythropoietin (EPO), a hormone released by the kidney that signals the bone marrow to produce more RBCs.
EPO production is influenced by chronic hypoxia, a long-term state of oxygen deprivation. For example, chronic lung disease, sleep apnea, or living at a high altitude can trigger the kidneys to produce more EPO. This leads to an increased RBC count, which enhances oxygen transport to the body's tissues.
Other causes of secondary erythrocytosis include:
- Tumors: Certain tumors, such as those of the kidneys, liver, brain, adrenal glands, or uterus, can secrete EPO.
- Decreased blood flow to the kidneys: Often due to tumors, cysts, or narrowing of surrounding arteries.
- Genetic disorders: Unlike those seen in primary causes, some mutations do not directly involve the bone marrow.
Lifestyle Factors
Secondary causes can also be lifestyle-induced, including:
- Smoking: This leads to oxygen deprivation and potential carbon monoxide poisoning, which can stimulate increased RBC production.
- Dehydration: Insufficient fluid (plasma) in the blood can lead to relative erythrocytosis, in which the number of RBCs is normal but appears elevated due to reduced plasma volume.
- Steroid use: Testosterone therapy, anabolic steroids, or other performance-enhancing drugs can increase RBC production.
Additional Testing and Biomarkers
Further workup is necessary to investigate the underlying cause upon detecting a high RBC count.
Biomarkers to Test
- Hematocrit: Included in the CBC, this test measures the percentage of RBCs in the blood. Elevated levels (>49% in men or >48% in women) are typically seen with erythrocytosis.
- Hemoglobin: Also included in the CBC, hemoglobin is a protein within RBCs that carries oxygen. High levels (>16.5 g/dL in men or >16.0 g/dL in women) are also typically seen with erythrocytosis.
- Erythropoietin: An EPO test helps providers differentiate between primary (low EPO) and secondary (high EPO) causes of high RBC count.
- Oxygen saturation: Measures the amount of oxygen carried by RBCs. Non-invasive measurement by pulse oximetry (a device that shines a light through the finger) is common; arterial blood sampling provides more precise readings. A saturation level below 92% suggests hypoxia (oxygen deprivation).
- Ferritin: Ferritin is a protein that indicates the body's iron storage capacity, with levels varying based on factors such as the underlying cause of erythrocytosis.
- JAK2 mutation test: JAK2 is a gene mutation seen in more than 95% of PV patients. Testing should only be considered when there is high clinical suspicion of this pathology.
Imaging Tests
Additional imaging tests may be necessary in specific cases:
- CT scan or MRI: Computerized tomography (CT) scan or magnetic resonance imaging (MRI) studies can detect EPO-producing tumors or other abnormalities.
- Bone marrow biopsy: Considered for definitive diagnosis when PV is suspected.
Depending on the individual case, other tests considered for secondary causes may include abdominal ultrasound, chest X-ray, echocardiogram, lung function tests, or sleep studies.
Diagnosis and Treatment
Given the wide range of contributing factors, accurately diagnosing the cause of high RBC count is required to determine the appropriate treatment.
Diagnostic Process
- Complete Blood Count (CBC): some text
- Blood smear: some text
- Visualized under a microscope to examine the number and shape of blood cells, identifying possible abnormalities.
- History: some text
- Thorough review including symptoms, past medical diagnoses, medications, and risk factors (e.g., smoking, hydration habits, steroid use).
- Physical Examination: some text
- Assess for signs of hypoxia, listen to heart and lung sounds, and check for signs of organ enlargement.
- Non-invasive testing:some text
- Pulse oximetry: Measures oxygen saturation.
- Serum EPO: Helps distinguish between primary and secondary causes.
- Comprehensive Metabolic Panel (CMP): Includes electrolytes, kidney, and liver function tests.
- Urinalysis: Checks for hematuria (blood in the urine) indicating kidney tumors or other issues.
- Testing for select cases: some text
- JAK2 mutation: Identifies mutations associated with PV.
- Imaging: CT or MRI to detect tumors or other abnormalities.
- Bone marrow biopsy: Provides definitive diagnosis in suspected PV cases.
The diagnostic approach combines patient and family history, physical examination, and various laboratory and imaging studies to guide appropriate testing based on clinical suspicion and findings.
Treatment Options
Properly managing associated conditions can help address secondary forms of erythrocytosis. For example:
- Chronic lung disease: Treatment may involve medications, pulmonary rehabilitation, or supplemental oxygen.
- Sleep apnea: Management may include lifestyle changes, using a CPAP machine, or surgical interventions.
Individuals with primary erythrocytosis, such as PV, require alternative methods:
- Phlebotomy: Therapeutic phlebotomy involves routine blood draws to control RBC counts and may also be applied in some cases of secondary origin.
- Medications: Certain drugs like hydroxyurea, interferon alfa, or ruxolitinib may be prescribed for PV patients to help reduce the number of blood cells. Low-dose aspirin may also be recommended for those at high risk of blood clots to prevent complications.
Living with a High RBC Count
Living with a high RBC count requires a holistic approach for the best outcomes.
Lifestyle Modification
Although high RBC counts cannot always be avoided, consider these factors to reduce the risk:
- Stay hydrated to maintain healthy blood volume. Avoid excessive caffeine intake, which can deplete fluids.
- Avoid smoking.
- Incorporate regular exercise to promote healthy blood flow.
- Avoid anabolic steroids and other performance-enhancing drugs.
- Avoid iron supplements, which can contribute to RBC production.
Regular Monitoring
Regular monitoring and follow-up tests are critical for managing a high RBC count and detecting potential complications early, such as blood clots or cardiovascular issues. This allows for timely interventions. Consistent testing also helps track changes in RBC levels and assess the effectiveness of treatments.
Medical providers may need to adjust treatment plans based on test results and symptoms. If RBC counts remain high or symptoms worsen, modifications might include changes in medication dosages, additional therapeutic phlebotomy sessions, or new lifestyle recommendations.
Conversely, treatment intensity may be reduced if RBC counts stabilize or improve. Continuous evaluation ensures the management plan is effective and tailored to the patient's evolving needs.
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Key Takeaways
- A high RBC count, also termed erythrocytosis or polycythemia, is an elevated number of red blood cells in the bloodstream.
- Common symptoms include fatigue, dizziness, and headaches. Severe complications include blood clots and stroke.
- High RBC counts can stem from primary causes like Polycythemia vera (PV), a bone marrow disorder, or secondary causes, such as chronic hypoxia, tumors, or lifestyle factors, including smoking and dehydration.
- Accurate diagnosis involves a combination of tests, including a Complete Blood Count (CBC) and erythropoietin (EPO) levels.
- Management strategies vary based on the cause and can involve therapeutic phlebotomy, medications, and lifestyle modifications.
- Regular monitoring and follow-up tests are essential to track RBC levels and detect complications early. Open communication with healthcare providers ensures effective management and timely intervention.
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