What is a complete blood count (CBC)?
Cancers diagnosed: All
Why performed: The CBC is a common screening test. It does not determine a specific type of cancer. The results may lead the physician to order other blood tests and imaging studies that determine the presence of cancer. Chemotherapy and radiation treatments may affect any or all of the tests that make up a CBC. Therefore, a CBC or any part of it is used to monitor treatment.
Patient preparation: No special preparation is needed.
Steps of the procedure: A small sample of blood is collected from a vein and placed in a tube. In children, blood may be obtained from a capillary in the heel or finger.
After the procedure: A small gauze or cotton ball is applied at the site of needle insertion. The patient is asked to apply pressure. The person collecting the blood observes the site for bleeding and may apply a bandage. The bandage may usually be removed in thirty to sixty minutes.
Risks: The risks of CBC include bleeding, bruising, hematoma (bleeding under the skin), fainting, light-headedness, or multiple needlesticks to obtain a sample.
Results: Normal CBC levels vary by the patient’s sex and age and the analyzer used. Each laboratory establishes a set of normal ranges based on this information. The physician receives a report of the test results with the normal values. CBC results may be higher or lower than normal depending on the type of cancer, treatment, any bleeding, or infectious processes taking place.
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