Red Blood Cell (RBC) Count

The red blood cell (RBC) count, also known as an erythrocyte count, is a test used to measure the number of red blood cells in the blood.

Purpose

The RBC count is used to:

• Diagnose and monitor conditions that affect red blood cell production, such as anemia, polycythemia, and bone marrow disorders
• Evaluate the effectiveness of treatments for these conditions
• Monitor patients with chronic diseases, such as kidney disease or cancer, that can affect red blood cell production

Procedure

A healthcare provider will typically perform a venipuncture, which involves:

• Inserting a needle into a vein in the arm to collect a blood sample
• Collecting the blood sample in a tube that contains an anticoagulant to prevent clotting
• Sending the sample to a laboratory for analysis

Analysis

In the laboratory, the RBC count is typically performed using an automated hematology analyzer, which:

• Counts the number of red blood cells in the sample
• Measures the size and shape of the red blood cells (mean corpuscular volume, MCV)
• Calculates the percentage of red blood cells in the sample (hematocrit, HCT)

Results

The results of an RBC count are typically reported as:

• RBC count: the number of red blood cells per microliter of blood (normal range: approximately 4.32-5.72 million cells/μL for adult men and 3.90-5.30 million cells/μL for adult women)
• MCV: the average size of the red blood cells (normal range: approximately 80-100 femtoliters, fL)
• HCT: the percentage of red blood cells in the sample (normal range: approximately 40.7-50.3% for adult men and 36.1-48.3% for adult women)

Abnormal Results

An abnormal RBC count can indicate a variety of conditions, including:

• Anemia (low RBC count)
• Polycythemia (high RBC count)
• Bone marrow disorders, such as leukemia or lymphoma
• Kidney disease or cancer that affects red blood cell production

Limitations and Considerations

The RBC count is a commonly used test, but it has some limitations and considerations:

• Results can be affected by factors such as dehydration, recent blood transfusions, or certain medications
• A single abnormal result should be confirmed with repeat testing and other diagnostic tests to determine the underlying cause

Frequently Asked Questions (FAQs)

What is a Red Blood Cell (RBC) count?
A test that measures the number of red blood cells in the blood.

Why is an RBC count performed?
To diagnose and monitor conditions such as anemia, bleeding disorders, and bone marrow disorders.

What is a normal RBC count range?
Typically around 4.32-5.72 million cells per microliter for males and 3.90-5.03 million cells per microliter for females.

How is an RBC count performed?
A blood sample is taken from a vein, usually in the arm, and sent to a laboratory for analysis.

What can affect RBC count results?
Various factors, including age, sex, altitude, and certain medical conditions.

Is an RBC count a definitive diagnostic test?
No, it is often used in conjunction with other tests to confirm a diagnosis.

Can an RBC count be performed on people of all ages?
Yes, but reference ranges may vary depending on age, particularly in children and infants.

Are there any risks associated with an RBC count?
Generally no, but minor risks include bleeding, bruising, or infection at the blood draw site.

How often is an RBC count repeated?
As necessary, depending on the underlying condition being monitored or diagnosed.

Can an RBC count be used to screen for certain diseases?
Yes, it may be used as a screening test for conditions such as anemia, but further testing is typically required for diagnosis.