The complete blood count: A guide for patients with cancer

Cancer chemotherapy and radiation therapy are used to damage or kill cancer cells. Some of the body's normal cells, including the blood cells, may also be damaged by these treatments. Some medicines can also slow down the making of blood cells. The good news is that your body can repair damaged normal cells. Most of the side effects of cancer treatment caused by the damage to normal cells only last for a short time, until the body has had time to repair the damage. This booklet will explain about the normal cells that can be damaged that are made in the bone marrow.

Bone marrow

Most types of blood cells are made in the bone marrow. The bone marrow is the soft, spongy tissue found in the center of the large bones like the pelvic bones, the breast bone, and the long leg bones. All cells made in the bone marrow start out as a single kind of cell called a stem cell. Depending on what type of cell the body needs, a stem cell can become one of three major types of blood cells, a red cell, a white cell, or a cell that makes platelets.

Blood cells

Red blood cells, also called erythrocytes, contain hemoglobin that gives red blood cells their color and carries oxygen from the lungs to the tissues. If the number of red blood cells is low, a person may feel tired or short of breath.

The white blood cells, or leukocytes, are part of the body's immune system. There are several types of white blood cells that help to prevent and fight infections.

The platelets or thrombocytes are tiny particles that help the blood to clot or stop bleeding when there is an injury. If the platelets are low, a patient may bleed or bruise easily.

Red blood cell count (RBC)

This test counts the number of red blood cells in a single drop (a microliter) of blood.

Normal ranges (vary by age and gender):

• Men: 4.5 to 6.2 million
• Women: 4.0 to 5.2 million

Total hemoglobin concentration

This test measures the grams of hemoglobin in a deciliter (100 milliliters) of blood.

Normal values are:

• Men: 13.2 to 17.7 g/dl
• Women: 11.9 to 15.5 g/dl

Any time that the hemoglobin level drops below 10 g/dl, a person is anemic.

Hematocrit

Hematocrit measures the percentage of red blood cells in the sample of blood.

Normal values (vary by age and gender):

• Men: 40% to 55%
• Women: 35% to 47%

Erythrocyte (RBC) tests

Three tests measure the size of the red blood cells and the amount of hemoglobin within each cell. Why are these tests done over and above the Hb and Hct?

• Mean corpuscular volume (MCV) measures the volume of red blood cells. Normal is 82 to 99 femtoliters.
• Mean corpuscular hemoglobin (MCH) measures the amount of hemoglobin in an average cell. Normal is 25 to 35 picograms.
• Mean corpuscular hemoglobin concentration (MCHC) measures the concentration of hemoglobin in red blood cells. Normal is 32% to 36%.

White blood cell count (WBC)

This test measures the number of white blood cells in a drop (microliter) of blood. A low WBC count may be due to chemotherapy, a viral infection, a toxic reaction, or a process in the bone marrow that limits the body’s ability to make normal WBCs. A high WBC count may result from an infection or leukemia. A person is at an increased risk of infection if his/her WBC count drops below 1,000 cells per microliter.

Normal values:

• Range from 3,700 to 10,500 (can be altered by exercise, stress, and disease)

WBC differential

This test tells the percentage of each type of white blood cell in the sample.

Normal values are:

If the total neutrophil count drops below 500 cells per microliter, a serious infection can develop. Another word used for neutrophils is segmented neutrophils or "segs."

Platelet count

This test measures the number of platelets in a drop (microliter) of blood. Platelet counts increase during strenuous activity, infections, cancers, and when the spleen has been removed. Platelet counts decrease just before a woman menstruates. A count below 50,000 can result in bleeding; below 5,000, patients are at risk of dangerous bleeding.

Normal values:

• 150,000 to 400,000 per microliter