Diagnostics
Complete Blood Count
What is a complete blood count (CBC)?
A complete blood count (CBC) is a very common blood test that helps doctors check the overall health of a patient. The CBC test looks at the levels of different types of cells in the blood, like red cells, white cells, and platelets. The results from this test help doctors check for many health issues, look for diseases, and decide on treatments.
Who conducts the CBC test?
An individual can visit a lab to give the blood sample or get the sample collected from home. The phlebotomist (medical professionals who work in medical labs, taking blood samples from patients) collects the blood sample and sends it to the laboratory for analysis.
Why CBC test is recommended?
A CBC is usually ordered as part of a routine check-up to monitor an existing medical condition or to investigate symptoms.
CBC may be necessary if an individual experiences the following symptoms:
- Presence of fever, nausea, and vomiting
- Inflammation is characterized by swelling and irritation anywhere in the body
- Unexplained bruising or bleeding
- Fatigue, dizziness, or weakness
- Joint pain
- Issues related to heart rate or blood pressure
How CBC test is performed?
- The phlebotomist or lab technician first cleans the area using an antiseptic alcohol wipe where the needle will be inserted. This area is often either inside the elbow or at the top of the hand.
- A tourniquet is tied around the upper arm to enhance the visibility and accessibility of the vein.
- A needle is then inserted into the vein, and a test tube is attached to collect the blood sample. The prick feels like a slight pinch or feels like an ant bite.
- Once the test tube is filled, the needle is removed, concluding the procedure.
- After removing the needle, a small bandage is applied over the puncture site to protect it. It is common to experience slight bruising at the puncture site following a blood draw.
What are the components of a complete blood count?
- Red Blood Cells (RBCs): RBCs carry oxygen throughout the body. The CBC measures parameters such as haemoglobin (Hb), haematocrit (Hct), and red blood cell count. Abnormal RBC levels can indicate conditions like anaemia or certain chronic diseases.
- White Blood Cells (WBCs): WBCs are part of the immune system and help fight infections. The CBC provides the total WBC count and may also give a breakdown of different types of WBCs. Abnormal WBC levels can indicate infections, inflammation, or certain blood disorders.
- Platelets: Platelets are essential for blood clotting and preventing excessive bleeding. The CBC measures platelet count. Abnormal platelet levels can indicate bleeding disorders or bone marrow disorders.
- Haemoglobin and Haematocrit: Haemoglobin is a protein in red blood cells that carries oxygen. Haematocrit measures the percentage of RBCs in the blood. Both values help evaluate anaemia or dehydration.
- Mean Corpuscular Volume (MCV): MCV measures the average size of RBCs. It can help determine the cause of anaemia and differentiate between different types of anaemia.
- Differential WBC Count: This provides the proportions of different types of WBCs (neutrophils, lymphocytes, monocytes, eosinophils, and basophils). It helps identify specific infections or abnormalities in the immune system.
By analyzing CBC results, doctors can gather valuable information about an individual’s health status, enabling them to offer suitable and targeted medical care.
Blood typing is particularly crucial in pregnant women. The child is likely to be Rh-positive if the mother is Rh-negative and the father is Rh-positive. In such cases, the mother may need to receive a medication known as RhoGAM. This medication prevents the mother’s body from producing antibodies that could attack the baby’s blood cells and destroy them. When red blood cells are broken down, they make bilirubin. This causes an infant to become yellow (jaundice). The bilirubin level in the infant’s blood may range from mild to dangerously high.
References
- American Association for Clinical Chemistry. (n.d.). Complete Blood Count (CBC). Available from https://labtestsonline.org/tests/complete-blood-count-cbc
- Mayo Clinic. (2022). Complete Blood Count (CBC). Available from https://www.mayoclinic.org/tests-procedures/complete-blood-count/about/pac-20384919
- Cleveland Clinic. Complete blood count. Available from: https://my.clevelandclinic.org/health/diagnostics/4053-complete-blood-count
- Complete blood count (CBC). Available from: https://medlineplus.gov/lab-tests/complete-blood-count-cbc/
