Diagnosis of cytopenia in the cancer patient requires a complete blood count (CBC) and the identification of any blood and bone marrow abnormalities.
Complete Blood Count
A complete blood count (CBC) is performed to identify anemia, neutropenia, or thrombocytopenia. A sample of the patient's blood is drawn and examined under a microscope to obtain the CBC.
Red blood cell count (RBC) is the number of red blood cells capable of carrying hemoglobin in a cubic millimeter of blood. The normal RBC for men is 4.5 to 6 million cubic millimeter; for women, 4 to 5.5 million per cubic millimeter. Reticulocytes (young red blood cell) are also counted.
White blood cell count (WBC) is the total number of all five types of white blood cells. The normal WBC for men and women is 5,000 to 10,000 per milliliter of blood.
Five types of cells are counted and then reported as a percentage of the WBC. This is called the differential. (Mast cells are not included because they are not present in the blood.) Typical reports show the normal range:
- Basophils < 1 percent
- Eosinophils 14 percent
- Lymphocytes 2040 percent
- Monocytes or macrophages 28 percent
- Neutrophils 5570 percent
Cell counts above or below the normal range are highlighted for the physician.
The normal platelet count ranges from 150,000 to 450,000 platelets per milliliter of blood.
Monitoring the Blood CountBecause chemotherapeutic agents adversely affect bone marrow cells, a complete blood count (CBC) is necessary prior to each treatment. The effects on bone marrow are temporary and normal functioning usually returns within 410 days.
Because mature red blood cells have a relatively long life (120 days), cell production usually resumes before symptoms of deficiency develop. White blood cells, however, have a life span of 1 to 3 days only. Those in circulation remain unaffected, but the production of new leukocytes may be slow, creating a period of increased risk for infection.
White blood cell production usually recovers before the next treatment. If it does not, treatment is delayed until the cell count increases sufficiently.
Thrombocytopenia (below normal platelet count of 15,000 to 300,000 per milliliter) and the risk of increased bleeding usually peaks 10 to 14 days following a course of chemotherapy. Damage to these cells is not permanent and their full recovery is expected within 2-weeks after treatment.
Bone Marrow Aspiration and Needle Biopsy
Both of these tests involve taking samples of bone marrow for examination under a microscope. Samples are usually obtained from the pelvic bone but may be taken from the breastbone.
The puncture site for marrow extraction from the pelvic bone is located in the lower back. Both procedures present a risk for bleeding at the puncture site and infection, although infection is rare.
AspirationBone marrow aspiration is performed with a thin aspirating needle (needle with a syringe) to obtain a sample of bone marrow fluid.
The puncture site is cleansed with antiseptic and then a local anesthetic is given to the patient. Once the anesthetic has taken effect, the aspirating needle is inserted into the bone. The plunger is then pulled to suction out a sample of bone marrow fluid into the syringe. The sample is put between glass slides for examination under a microscope.
Pressure is applied to the puncture site to stop any bleeding, and then the wound is covered with a bandage.
Needle biopsyA bone marrow biopsy needle is used to remove a sample of bone marrow tissue. Sometimes marrow aspirate is taken before the biopsy is performed.
First, the puncture site is cleansed with antiseptic, and then a local anesthetic is given to the patient. Once the anesthetic has taken effect, a small incision is made in the lower back. The biopsy needle is inserted through the incision and into the bone. The solid core of the needle is removed from the shaft, and the needle turned back and forth to collect a tissue sample.
Pressure is applied to the puncture site to stop any bleeding. The wound is then covered with a bandage.