Complete blood count (CBC)
A Complete Blood Count (CBC), also known as a hemogram, is a comprehensive blood test that evaluates various components of blood, including red blood cells, white blood cells, and platelets. The CBC provides valuable information, such as the total white blood cell count and the distribution of different white cell types, as well as measurements related to red cells, like hemoglobin levels and hematocrit. This test is typically performed using an automated hematology analyzer, with a small blood sample collected from a vein, or in children, from a capillary in the heel or finger.
CBCs are commonly conducted during routine check-ups to screen for health conditions, including anemia, leukemia, and autoimmune disorders. While a CBC can indicate potential health issues, it does not provide a definitive diagnosis, so further testing may be necessary if results are abnormal. This test is also crucial for monitoring patients undergoing cancer treatment, as these therapies can significantly impact blood-cell production.
Preparation for a CBC does not require any special steps, and while the procedure is generally safe, some risks include bleeding and bruising at the sample site. The results of a CBC can vary based on age, sex, and the specific laboratory performing the test, with each facility establishing its normal ranges. If abnormalities are found, physicians may recommend additional screenings or tests to clarify the patient's health status.
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Complete blood count (CBC)
ALSO KNOWN AS: Hemogram
DEFINITION: A complete blood count (CBC) is a group of blood tests that provides information about red cells, white cells, and platelets. The tests included are white cell count (WBC); white cell differential (the percentage of each of the white cell types neutrophils, lymphocytes, monocytes, eosinophils, and basophils); red cell count (RBC); hemoglobin (HGB); hematocrit (HCT); platelet count (PLT); mean corpuscular volume (MCV); mean corpuscular hemoglobin (MCH); mean corpuscular hemoglobin concentration (MCHC); mean platelet volume (MPV); and red cell distribution width (RDW).
The test is performed using whole blood on an automated hematology analyzer. The HCT, MCH, and MCHC are calculated from the measured results of the RBC, HGB, and MCV. MPV is the average size of the platelets. RDW is a calculation based on the red cell indicating the variation in red cell size. A technologist may make a thin smear of the sample on a glass slide, stain it with special dyes, and examine the cells using a microscope.
Why performed: The CBC is a common screening test that may be done at a routine check-up. It helps identify the presence of conditions that affect the blood cells, such as anemia, leukemia, or autoimmune disorders. A CBC usually does not produce a definitive diagnosis, so if results are abnormal, further tests may be ordered. When a patient is diagnosed with a blood-related condition, he or she may receive regular CBCs to monitor the condition. CBCs are also used to monitor cancer treatment, as chemotherapy and radiation treatments may affect various aspects of blood-cell production.
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 gathered values. CBC results may be higher or lower than normal depending on health conditions, cancer treatments, any bleeding, or infectious processes taking place. If abnormalities exist, further screenings or tests may be recommended.
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