How A Complete Blood Count (CBC) Factors Into Testing For Cancer

Feb 21, 2022

Although doctors do not rely on blood tests alone to diagnose patients with cancers, they do use these screenings to understand what is happening inside the body. A complete blood count (CBC) is one test that many physicians order for patients they suspect may have cancer. CBC tests look at blood cells to help healthcare providers formulate a cancer diagnosis. Learn how these routine blood tests factor into cancer screening from TOPLAB®.

What Are CBC Tests?

CBCs assess the number of different types of cells in a blood sample. Results showing abnormal cells, or an above- or below-average amount for a particular type of blood cell, may indicate the person has blood cancer. If a person already has cancer, blood work can help physicians see how the cancerous cells affect their organs. There are three main components that CBC tests measure, including:

Red Blood Cell Count

Also referred to as an erythrocyte count, this test measures the number of red blood cells in the sample. Red blood cells transmit oxygen to different areas in the body. There are multiple approaches to evaluating red blood cells, but the two most frequently used are hemoglobin and hematocrit. Hemoglobin is the amount of the protein in red blood cells that carries oxygen, while hematocrit is the fraction of the blood made up of red blood cells. 

White Blood Cell Count

A white blood cell count – or leukocyte count – assesses the total number of white blood cells in a sample. These cells fight against bacteria, viruses, and similar diseases to safeguard the body from infection. Some white blood cells also combat cancerous cells.

If a doctor wants to look at specific white blood cells, they may order a differential. There are five primary kinds of white blood cells in the body, including Basophils, Eosinophils, Lymphocytes, Monocytes, and Neutrophils. Since each cell type plays a unique role in defending the body against illness, this blood work can help doctors identify cancerous cells or determine the effects of cancer.

Platelet Count

Platelet counts calculate the number of platelets found in a blood sample. Also known as thrombocytes, platelets are small blood cells originating in the bone marrow. They help the body create clots to stop bleeding.

What Are Normal CBC Test Results?

After a CBC test, the lab technician will compare the results to a range of normal CBC numbers. According to the Mayo Clinic, the healthy ranges of CBC results for each blood cell type are:

  • White blood cell count: 3.4-9.6 billion cells per liter for men and women
  • Red blood cell count: 4.35-5.65 trillion cells per liter for men, 3.92-5.13 trillion cells per liter for women
  • Hemoglobin: 132-166 grams per liter for men, 116-150 grams per liter for women
  • Hematocrit: 38.3-48.6% for men, 35.5-44.9% for women
  • Platelet count: 135-317 billion per liter for men, 157-371 billion per liter for women

What Do Abnormal CBC Test Results Mean?

Test results that fall outside the normal range do not mean a person has cancer. A patient’s gender, age, and medical history can impact their test, and a noncancerous medical condition can lead to atypical results. That said, some abnormal CBC test results may indicate the presence of cancer, including:

  • Low red blood cell count: People with anemia have a below-average number of red blood cells. A low red blood cell count may point toward bone marrow cancer, which often causes anemia. It also can signify the effects of chemotherapy and radiation therapy as these cancer treatments can lower red blood cell counts.
  • Low white blood cell count: Blood and bone marrow cancers such as lymphoma, leukemia, and multiple myeloma can lower a person’s white blood cell count. Chemotherapy and similar cancer treatments also can have this effect.
  • Differential white blood cell counts: Heightened levels of lymphocytes or monocytes may suggest a person has cancer. Some cancers and treatments can cause below-average neutrophils, leading to neutropenia. This condition increases the chances the sufferer will contract a bacterial infection.
  • Low platelet count: Besides red blood cells, chemotherapy and radiation therapy also can diminish platelet counts. Additionally, certain bone marrow cancers can reduce the number of platelets in the blood.

What Follows This Cancer Blood Test?

As mentioned, doctors do not usually use CBCs to diagnose cancer. If the results fall outside the normal range, the provider may conduct other cancer screenings to develop a diagnosis, such as surgical pathology testing. If a person with cancer receives adverse results from a CBC test, they may need to modify their current treatment plan.

Obtain Cancer Blood Testing From TOPLAB®

Patients seeking a CBC test to screen for cancer should look no further than TOPLAB®. We use the most updated technologies at our small laboratory to deliver fast and accurate results for various blood tests, including CBCs. Contact us at 877-355-3580 to learn more about blood work for people in NJ and nationwide, or book an appointment online today.