What is a CBC Blood Test?

A Complete Blood Cell Count (CBC) blood test is a common medical test that measures different parts of your blood. It gives important information about your health by analyzing three main types of cells:

• Red Blood Cells (RBCs): These cells carry oxygen from your lungs to the rest of your body and bring carbon dioxide back to your lungs to be exhaled. The CBC measures the number of red blood cells, as well as related components like:
  • Hemoglobin: The protein in red blood cells that carries oxygen.
  • Hematocrit: The proportion of red blood cells in your blood.
  • Mean Corpuscular Volume (MCV): The average size of your red blood cells.
  • Mean Corpuscular Hemoglobin (MCH): The average amount of hemoglobin in each red blood cell.
• White Blood Cells (WBCs): These cells are part of your immune system and help fight infections. The CBC counts the total number of white blood cells in your blood.
• Platelets: These small cell fragments help your blood clot, stopping bleeding when you get a cut. The CBC measures the number of platelets you have.

In addition to these counts, a CBC provides other details about the shape, size, and health of these cells, which can help doctors diagnose various conditions.

Key Components Measured in a CBC

• Red Blood Cell Count (RBC): Indicates the number of red blood cells in your blood.
• White Blood Cell Count (WBC): Shows the total number of white blood cells in your blood.
• Platelet Count: Reflects the number of platelets in your blood.
• Hemoglobin (Hgb): The amount of the oxygen-carrying protein in your red blood cells.
• Hematocrit (Hct): The proportion of your blood that is made up of red blood cells.
• Mean Corpuscular Volume (MCV): The average size of your red blood cells.
• Mean Corpuscular Hemoglobin (MCH): The average amount of hemoglobin in your red blood cells.
• Mean Corpuscular Hemoglobin Concentration (MCHC): The average concentration of hemoglobin in your red blood cells.
• Red Cell Distribution Width (RDW): A measure of the variation in the size of your red blood cells.

Each of these components provides clues about your overall health and helps your doctor identify any potential health issues. For example, a low hemoglobin level might suggest anemia, while a high white blood cell count could indicate an infection.

What is a CBC with Differential?

A CBC with differential is an extension of the standard CBC blood test that provides more detailed information about your white blood cells. This test not only counts the total number of white blood cells but also breaks down the count into five different types of white blood cells. Each type has a unique role in your immune system and helps your body fight different kinds of infections and diseases. Understanding the levels and proportions of these cells can give your doctor more specific information about your health.

Types of White Blood Cells Measured in a CBC with Differential:

• Neutrophils: These are the most common type of white blood cells and are your body's first line of defense against bacterial infections. They quickly respond to infections by destroying bacteria and other harmful organisms.
  • High Neutrophil Count: Often indicates a bacterial infection, inflammation, or stress.
  • Low Neutrophil Count: Could suggest a severe infection that has overwhelmed your immune system, or conditions like bone marrow disorders.
• Lymphocytes: These cells are essential for your immune system. There are two main types of lymphocytes: B cells and T cells. B cells produce antibodies to fight infections, while T cells destroy infected or cancerous cells.
  • High Lymphocyte Count: May indicate a viral infection or chronic inflammatory condition.
  • Low Lymphocyte Count: Can be seen in cases of severe illness, immune deficiency, or certain types of cancer.
• Monocytes: These cells are responsible for engulfing and digesting foreign substances in the body, including bacteria and dead or damaged cells.
  • High Monocyte Count: Often seen in chronic infections, autoimmune diseases, or certain cancers.
  • Low Monocyte Count: Rare and usually not a concern unless in combination with other abnormal counts.
• Eosinophils: These cells combat parasites and play a role in allergic reactions.
  • High Eosinophil Count: Commonly associated with allergic reactions, asthma, or parasitic infections.
  • Low Eosinophil Count: Typically not a concern as they naturally exist in lower numbers.
• Basophils: These are the least common white blood cells and are involved in allergic reactions and inflammatory responses.
  • High Basophil Count: Can indicate allergic reactions, chronic inflammation, or certain types of blood disorders.
  • Low Basophil Count: Usually not a concern as they are normally found in low numbers.

Why is a CBC with Differential Performed?

A CBC with differential is often ordered when a doctor needs a more comprehensive picture of your immune system's health. This test can help in diagnosing:

• Infections: By identifying whether the infection is bacterial, viral, or parasitic.
• Allergic Reactions: Through elevated eosinophil counts.
• Blood Disorders: Such as leukemia or lymphoma, by showing abnormal levels and types of white blood cells.
• Immune System Disorders: Indicated by abnormal levels of lymphocytes or neutrophils.

By providing detailed information about the different types of white blood cells, a CBC with differential helps doctors make more accurate diagnoses and tailor treatment plans more effectively.

Why is a CBC Blood Test Performed?

A CBC blood test is a versatile tool used for various medical purposes. Here are the main reasons why doctors order this test:

Diagnostic Purposes

1. Anemia: This condition occurs when you have too few red blood cells or not enough hemoglobin in your blood. Symptoms include fatigue, weakness, and shortness of breath. A CBC can help diagnose different types of anemia by measuring your red blood cells and hemoglobin levels.
2. Infections: By analyzing your white blood cell count, doctors can determine if your body is fighting an infection. A high white blood cell count usually indicates an infection, while a low count can suggest a severe infection or other immune system issues.
3. Inflammation: Inflammatory conditions like rheumatoid arthritis or lupus can cause changes in your blood cell counts, which can be detected with a CBC.
4. Bleeding Disorders: A low platelet count can suggest a bleeding disorder, where your blood doesn't clot properly, leading to excessive bruising or bleeding.

Monitoring Existing Conditions

1. Chronic Diseases: For people with conditions like chronic kidney disease, heart disease, or diabetes, regular CBC tests help monitor their overall health and detect any changes that might indicate complications.
2. Chemotherapy: Patients undergoing chemotherapy for cancer often have regular CBC tests to monitor their blood cell counts, as chemotherapy can affect the production of blood cells in the bone marrow.
3. Medication Effects: Some medications can impact blood cell counts. Regular CBC tests help doctors ensure these medications are not causing harmful side effects.

Routine Health Checkups and Preventive Care

1. General Health Monitoring: A CBC is often part of a routine checkup. It provides a snapshot of your overall health and can detect issues before symptoms appear.
2. Pre-Surgical Evaluation: Before surgery, doctors may order a CBC to ensure you have no underlying conditions that could complicate the procedure.

How to Prepare for a CBC Blood Test

Preparing for a Complete Blood Cell Count (CBC) blood test is straightforward, but following a few simple guidelines can help ensure accurate results. Here are the steps to take before your test:

Fasting and Dietary Considerations

1. Fasting: Generally, a CBC test does not require fasting, meaning you can eat and drink normally before the test. However, if your doctor has ordered other blood tests along with the CBC, you might need to fast for a certain period, usually 8-12 hours. Always follow your doctor's specific instructions.
2. Diet: There are no special dietary restrictions before a CBC test. Eating a balanced meal and staying hydrated is recommended.

Medication Adjustments

1. Medications: Inform your doctor about all the medications you are taking, including prescription drugs, over-the-counter medicines, and supplements. Some medications can affect blood cell counts, and your doctor might advise you to adjust your medication schedule before the test.
2. Blood Thinners: If you are on blood thinners, your doctor needs to know as these can affect your platelet count and clotting ability.

Informing Your Healthcare Provider

1. Existing Health Conditions: Let your healthcare provider know about any chronic illnesses or recent infections, as these can influence your CBC results.
2. Symptoms: Report any symptoms you are experiencing, such as fatigue, fever, or unusual bleeding, as these can help your doctor interpret your test results more accurately.

Understanding the Results

Once your Complete Blood Cell Count (CBC) test is complete, your doctor will review the results. Here's how to understand what those results mean and what they might indicate about your health.

Normal Ranges for Different Components

The normal ranges can vary slightly depending on the lab, but generally, they are as follows:

• Red Blood Cell Count (RBC):
  • Men: 4.7 to 6.1 million cells per microliter
  • Women: 4.2 to 5.4 million cells per microliter
• White Blood Cell Count (WBC): 4,500 to 11,000 cells per microliter
• Platelet Count: 150,000 to 450,000 platelets per microliter
• Hemoglobin (Hgb):
  • Men: 13.8 to 17.2 grams per deciliter
  • Women: 12.1 to 15.1 grams per deciliter
• Hematocrit (Hct):
  • Men: 40.7% to 50.3%
  • Women: 36.1% to 44.3%
• Mean Corpuscular Volume (MCV): 80 to 100 femtoliters
• Mean Corpuscular Hemoglobin (MCH): 27 to 31 picograms per cell
• Mean Corpuscular Hemoglobin Concentration (MCHC): 32 to 36 grams per deciliter
• Red Cell Distribution Width (RDW): 11% to 15%

Interpretation of Abnormal Results

• Red Blood Cells (RBCs)
  • High RBC Count: This condition is known as polycythemia. It might indicate dehydration, living at high altitudes, or conditions that cause the body to produce too many red blood cells.
  • Low RBC Count: Known as anemia, this can result from blood loss, nutritional deficiencies (like low iron, vitamin B12, or folate), or bone marrow problems.
• White Blood Cells (WBCs)
  • High WBC Count: Called leukocytosis, it may indicate an infection, inflammation, an immune system disorder, or certain types of leukemia.
  • Low WBC Count: Known as leukopenia, it can be caused by severe infections, bone marrow disorders, autoimmune diseases, or the side effects of medications like chemotherapy.
• Platelets
  • High Platelet Count: Called thrombocytosis, this might be due to bone marrow disorders, inflammation, or certain cancers.
  • Low Platelet Count: Known as thrombocytopenia, this can result from bone marrow problems, autoimmune diseases, infections, or the use of certain medications.
• Hemoglobin (Hgb) and Hematocrit (Hct)
  • High Levels: Can be a sign of dehydration, smoking, living at high altitudes, or certain diseases.
  • Low Levels: Often indicate anemia, which could be due to various causes including nutritional deficiencies, chronic diseases, or bone marrow problems.
• Mean Corpuscular Volume (MCV)
  • High MCV: Indicates larger than normal red blood cells (macrocytic anemia), which can be caused by vitamin B12 or folate deficiency.
  • Low MCV: Indicates smaller than normal red blood cells (microcytic anemia), which can be due to iron deficiency or certain genetic conditions.
• Mean Corpuscular Hemoglobin (MCH) and Mean Corpuscular Hemoglobin Concentration (MCHC)
  • Abnormal Levels: Can provide further information about the type of anemia you might have, helping doctors pinpoint the cause.
• Red Cell Distribution Width (RDW)
  • High RDW: Indicates a large variation in the size of red blood cells, which can help diagnose different types of anemia.

Factors that Can Affect Results

Several factors can influence CBC results:

• Dehydration: Can falsely elevate RBC, hemoglobin, and hematocrit levels.
• Recent Illness or Infection: Can affect white blood cell counts.
• Medications: Certain drugs can impact blood cell counts, either increasing or decreasing them.
• Stress: Both physical and emotional stress can temporarily change blood cell counts.

If any of your CBC results are abnormal, your doctor might recommend additional tests to find the underlying cause. For example, if you have a low red blood cell count, further tests might be needed to check for iron deficiency or other nutritional issues.

Cost of Testing

CBC blood test is part of many of the panels we offer at TeleTest. For those in Canada, provincial insurance such as OHIP will usually cover the cost of CBC blood tests if it's medically necessary. If you do not have insurance coverage, it is $15 to $20 at most lab providers.

Disclaimer: This blog post is intended for educational purposes only and should not be taken as medical advice. Always consult your healthcare provider for personal health concerns.