What is a CBC Blood Test?
CBC blood test or complete blood test is one of the important and frequently conducted diagnostic test to estimates different blood cells component to evaluate general health condition or detecting different disorders including anemia, leukemia, sickle cells disorder and presence of infection. The included blood cells components , which are estimated by CBC blood test are:
- WBC (White blood cell or leukocyte) count: The WBC provides defensive mechanism of the body. It fight against invading infectious agent and some of them can act against cancerous cells. The total WBC count is usually lesser than the RBC count.
- Differential leukocyte count (DLC; differential white blood cell types or WBC differential): This test is performed to estimate the different types of WBCs. Mainly five types of WBCs are present in the human body, including Neutrophils, Lymphocytes, Monocytes, Eosinophils and Basophils. Each of them has a different role in body defensive mechanism.
- RBC (Red blood cell or erythrocytes) counts: One of the important function of RBCs are transportation of oxygen. Low or high number of RBCs are provided different abnormality in the body. Hematocrit (HCT) and Hemoglobin(Hgb) estimation are included in the RBC count.
- Red cell distribution width (RDW): This is a measure or the laboratory counting process of the size inconsistency of circulating Red Blood Cells (RBCs) or erythrocytes
- Hematocrit [(HCT); packed cell volume, PCV)]: The volume of red blood cells is measured by conducting this test. If the laboratory test result shows Hematocrit 37, then it denotes 37% total blood volume is made up of RBCs.
- Hemoglobin(Hgb) estimation: Hemoglobin is one of the chief components of RBCs and responsible for transportation of oxygen. Estimation of Hemoglobin helps to understand the oxygen carrying capacity of blood from the collected sample.
- Mean corpuscular hemoglobin (MCH): This test provides the size of the RBCs.
- Mean corpuscular volume (MCV): This value shows the total hemoglobin amount in an average red blood cell.
- Mean corpuscular hemoglobin concentration(MCHC): This can measure the hemoglobin concentration in an average red blood cell.
- Platelet count: Platelets are the blood cell component responsible for blood clotting. This tiny cells amount is very important for testing clotting disorders.
- Mean Platelet Volume (MPV): This test is conducted for estimating the average volume or amount of platelets.(1, 2)
The complete blood cell count is not only helping to detect the leukemia, but also helps to evaluate the spreading of cancer cells in the bone marrow and physiological reaction of cancer patient with cancer therapy.
How it is performed?
This test is conducted by collecting the blood sample from the person. The collected amount of blood is very low, only few milliliters or one to two teaspoonful. This test is conducted in every healthcare setup including clinical laboratory, hospitals and even in the doctor’s clinic. The test procedure is as follows:
- Bind an expandable band around the upper arm position to restrict the blood flow. This procedure make the easy visibility of the vein , as it thickens up and insertion of needles becomes easier.
- The site of the injection should wipe up with alcohol swab for avoiding infection.
- Disposable needle then inserted into the vein. Sometimes more than one prick is required, if the puncture is not made in vein.
- For collection of blood, a tube is attached to the syringe.
- When sufficient amount of blood is collected in the tube for conducting the test, then removes the band.
- Put a cotton ball or gauze piece at the injection site before removing the needle and press for a short vial for stoppage of bleeding.(2,3,4)
CBC Blood Test normal values
The included normal values of different sub-parameters are as follows:
The normal range slightly varies from laboratory to laboratory due to technological variations. Generally, this range is in between 4,300 and 10,800 cmm (cells per cubic millimeter) or it can also referred as 4.3 to 10.8 x 109 cells per liter in international unit.
Differential count of WBC
For measuring the different WBCs, a machine is used for automated result and this provides the percentage of each type of WBCs. Alternatively, manual count is also conducted by preparing a glass slide with blood smear and examine under a microscope in a laboratory.
- Neutrophils – 56% or 1800-7800 per microliter
- Lymphocytes – 34% or 1000-4800 per microliter
- Monocytes – 4% or 0-800 per microliter
- Eosinophils – 2.7% or 0-450 per microliter
- Basophils- 0.3% or 0-200 per microliter
RBC (Red blood cell or erythrocytes) counts
The normal range slightly varies from laboratory to laboratory due to technological variations. Generally, this range is in between 4.2 to 5.9 million cells/cmm. or it can also referred as 4.2 to 5.9 x 1012 cells per liter in international unit.
The normal range is slightly varied with gender. Generally this range is in between 13 to 18 grams per deciliter for men and 12 to 16 for women or it can also refer 8.1 to 11.2 millimoles/liter for men and 7.4 to 9.9 for women in international units.
The normal range is slightly varies with gender. Generally, this range is in between from approximately 45% to 52% for men and 37% to 48% for women.
Mean corpuscular volume (MCV)
This value is calculated by the hematocrit and red cell count. The normal range is in between 80 to 100 femtoliters (a fraction of one millionth of a liter).
Mean Corpuscular Hemoglobin (MCH)
Normal range is 27 to 32 picograms.
Mean corpuscular hemoglobin concentration (MCHC)
Normal range is 32% to 36%. This value is derived from hemoglobin concentration.
Red Cell Distribution Width (RDW)
Normal range is 11 to 15.
The normal range slightly varies from laboratory to laboratory due to technological variations. Generally. this range is in between 150,000 to 400,000/ cmm (150 to 400 x 109/liter).
Abnormal values seen in (high & Low)
Every parameter of CBC has high or low level and it indicates different disorders, which in can be illustrated in the following pattern:
Low WBC count
The usual disorders associated with this are:
- Disorder or damage in bone marrow
- Autoimmune diseases
- Nutritional deficiencies
- Lymphoma, leukemia, multiple myeloma.
- Immune system disorder including AIDS or HIV.
High WBCs count
The usual disorders associated with this are:
- Bacterial or viral infection
- Tissue injury including burns, cardiac attack
- Physical and mental stress.
Abnormality in differential WBC count
This is almost similar as abnormal disease conditions associated with high and low WBCs disorders.
Low RBCs count
- Acute or chronic hemorrhage
- Dietary insufficiency (vitamin B12, folate deficiency and iron deficiency )
- Disorders or damage bone marrow
- Chronic inflammatory disease
- Chronic renal disease
High RBC count
- Pulmonary or lung disorders
- Tumor in kidney
- living at high altitude
- Genetic disorder
- Bone marrow disorder
- Polycythemia vera—a rare disease
Low platelet count also known as thrombocytopenia
- Viral infection
- Liver cirrhosis
- Rocky mountain spotted fever
- Certain medication like quinidine, acetaminophen, sulfa drugs
- Platelet autoantibody
- Autoimmune disorders
- Leukemia, lymphoma
- Chemo or radiation therapy
High platelet count or also known as thrombocytosis
- Lung cancer, gastrointestinal cancer, breast cancer, ovarian cancer and lymphoma
- Rheumatoid arthritis,
- IBS (inflammatory bowel disease)
- Myeloproliferative disorder
- Anaemia (iron deficiency anemia, hemolytic anemia (2,3)
- Mayo Clinic Staff (2014), Complete blood count (CBC); Retrieve from: http://www.mayoclinic.org/tests-procedures/complete-blood-count/basics/what-you-can-expect/prc-20014088
- Siamak N. Nabili, (2016), Complete Blood Count (CBC); Retrieve from: http://www.medicinenet.com/complete_blood_count/page4.htm http://www.medicinenet.com/complete_blood_count/page4.htm
- Roberta B. Carey (2015), Complete Blood Count; Retrieve from: https://labtestsonline.org/understanding/analytes/cbc/tab/test/
- WebMD Medical Reference from Healthwise (2014); Complete Blood Count (CBC); Retrieve from: http://www.webmd.com/a-to-z-guides/complete-blood-count-cbc?page=3
- Net Editorial Board (2015); Complete Blood Count Tests; Retrieve from:http://www.cancer.net/navigating-cancer-care/diagnosing-cancer/reports-and-results/complete-blood-count-tests