Comprehensive Blood Count

General Description

The comprehensive blood count is one of the most important tests in a complete blood analysis. This test is carried out to count and observe both the size and shape of the blood's corpuscular elements, which are red blood cells, white blood cells, and platelets.

By studying the characteristics of the blood, which circulates throughout the body mainly transporting oxygen and carbon dioxide, relevant information is obtained about a person’s overall health as well as indications of a wide range of diseases.

The main aspects of a comprehensive blood count (CBC) and the diseases it can detect are:

Red Blood Cell Series: study of the quantity and characteristics of red blood cells.

• Red Blood Cells: count of the number of cells, which, if altered, may indicate dehydration, anemia, leukemia, or bleeding.
• Hematocrit: establishes the percentage of red blood cells in relation to the total blood volume. It may indicate dehydration or anemia.
• Hemoglobin: establishes the levels of this protein responsible for transporting oxygen. When abnormal, it may suggest liver disease, thalassemia, polycythemia vera, or lung disease.
• Mean Corpuscular Volume (MCV): checks the size of red blood cells, which can be altered due to alcoholism, hypothyroidism, or folic acid deficiencies.
• Mean Corpuscular Hemoglobin (MCH): provides information about the amount of hemoglobin in red blood cells on average.

White Blood Cell Series: evaluates the status of white blood cells. It is useful for diagnosing infections or leukemia.

• Leukocytes: total count of white blood cells. When altered, it may suggest lymphoma, leukemia, or multiple myeloma.
• Neutrophils: counts this type of white blood cell, as an excessive number can clearly indicate a bacterial infection.
• Lymphocytes: counts this class of white blood cells, which, if elevated, often indicates a viral infection.
• Monocytes: establishes the quantity of macrophage-type white blood cells that defend the body against external agents. Elevated values may suggest infection, autoimmune disease, or neoplastic blood disorders.
• Eosinophils: counts the number of white blood cells, which, if high, is usually due to an allergic reaction or parasitic infection.
• Basophils: an elevated count is also related to allergies.

Platelet System: measures the blood's ability to clot.

• Platelets: establishes the number of platelets in the blood. Altered results may indicate various types of thrombophilias.
• Activated Partial Thromboplastin Time (aPTT): checks the time it takes for the blood to clot.
• Prothrombin Time (PT): establishes how long it takes for the blood to form a clot.
• Fibrinogen: provides information about the quantity of this protein, which helps platelets bind together to stop bleeding.

When Is It Indicated?

A comprehensive blood count is part of routine health tests for healthy patients. It is also requested when there is suspicion of the presence of a disease in patients showing symptoms like weakness, fatigue, swelling, excessive bleeding, bruising tendencies, or unexplained fever.

Other uses of the comprehensive blood count include monitoring already diagnosed diseases or tracking treatments that may alter the characteristics of blood cells, such as chemotherapy.

How Is It Performed?

To perform a comprehensive blood count, a blood sample is required, which is obtained using a needle attached to a syringe. The necessary amount for this test is usually 10 cc, though sometimes more is needed.

Typically, purple-top tubes are used for blood counts, as they contain ethylenediaminetetraacetic acid (EDTA) to prevent clotting during storage and transport. Once in the laboratory, the blood is centrifuged to separate the serum and cells. Finally, a glass slide is prepared with a small amount of cells or serum to observe their shape and size under a microscope, count them, and observe their behavior.

Risks

The comprehensive blood count itself poses no health risk, but the extraction procedure may cause side effects such as bruising at the puncture site or dizziness due to blood loss. Both are usually mild complications that resolve quickly without the need for medical intervention.

What to Expect from a Comprehensive Blood Count

To collect the blood sample, it is recommended that the patient wear short sleeves or easy-to-remove clothing, as the arm must be exposed. During the procedure, the patient remains seated or slightly reclined on a cot.

After disinfecting the area, usually the inside of the elbow, a tourniquet is placed on the arm to make blood flow more easily. The needle is then inserted into the selected vein, and blood is drawn by operating the syringe plunger after removing the tourniquet.

To reduce the risk of bruising, a sterile gauze is applied to the puncture site, which should be pressed for a few minutes. In the following hours, it is recommended to drink fluids to help the body replenish the blood drawn.

The procedure typically takes no more than five minutes, after which the patient can resume their normal activities.

The report with the results can be picked up a week after the sample was taken.

Specialties That Request a Comprehensive Blood Count

The comprehensive blood count is a useful tool in nearly all medical specialties. It is performed by hematologists.