Part one – Deferential White Blood Cells count (Diff. WBCs Count) and microscopic examination of Well Stained Blood Film
Also known as: Leukocyte Differential Count; Peripheral Differential; WBC Count Differential; Diff Formal name: White Blood Cell Differential
In part one, we will study the method of the differential WBCs count and the examination of RBCs in the blood film and the examination of WBCS will be in the next part.
1) Aim and the value of the test:
White Blood cells are the cells produced in the bone marrow by the stem cells to fight in antigens (i.e. foreign bodies or cells in the body)
===> Types of WBCs:
1) Granulocytes: which divided into 3 types:
- Neutrophils (neu) they engulf and destroy bacteria or sometimes fungi that cause inflammation.
- Eosinophils (eos) respond to infections caused by parasites and play a role in allergic reactions (hypersensitivities)
- Basophils thought to be involved in allergic reactions
2) Lymphocytes They are divided into three types, but the differential does not distinguish among them and The differential counts and reports all lymphocytes together. (Separate specialized testing must be done to differentiate the three types):
- B lymphocytes (B cells)
- They are antibody-producing cells that are essential for acquired, antigen-specific immune responses.
- Fully mature B-cells are called plasma cells that produce antibodies, immune proteins that target and destroy bacteria, viruses and other “non-self” foreign antigens.
- T lymphocytes (T cells)
- Some T cells help the body distinguish between “self” and “non-self” antigens. Others initiate and control the extent of an immune response, boosting it as needed and then slowing it as the condition resolves.
- Other types of T cells directly attack and neutralize virus-infected or cancerous cells.
- Natural killer cells (NK cells) directly attack and kill abnormal cells such as cancer cells or those infected with a virus.
3) Monocytes (mono), similar to neutrophils, move to an area of infection and engulf and destroy bacteria. They are associated more often with chronic rather than acute infections. They are also involved in tissue repair and other functions involving the immune system.
When an antigen enters your body, the immune system starts to produce and release the army of the WBCs to fight and protect you according to the type of the antigen leading to increment or decrement of the WBCs number in the blood according to the condition
Also, if there is an illness in your immune system you, or cancer in the blood (leukemia), the number of the WBCs will be affected
Thus, this test totals the number of each type and determines if the cells are present in normal proportion to one another, if one cell type is increased or decreased, or if immature cells are present. This information is useful in helping to diagnose the specific cause of an illness, such as:
- Infections caused by bacteria, viruses, fungi or parasites
- Allergies, asthma
- Immune disorders (e.g., autoimmune disorders, immune deficiency)
Some diseases trigger a response by the immune system that causes an increase in certain types of WBCs. A differential may give clues to the specific cause of that immune response. For example, it may help determine whether an infection is caused by bacteria or by viruses.
Other conditions affect the production of certain WBCs by the bone marrow or their survival in the circulation, resulting in either an increase or decrease in their number. A differential informs the doctor as to which type of WBC is low or high.
Also during differential counting of WBCs, the morphology of RBCs and platelets are examined and presence of any parasites as well this leads to diagnose many diseases.
2) When this test is required?
A differential may be included as part of the CBC when someone has general signs and symptoms of an infection and/or inflammation, such as:
- Fever, chills
- Body aches, pain
- A variety of other signs and symptoms, depending on the site of suspected infection or inflammation
Testing may be performed when there are signs and symptoms that the doctor thinks may be related to a blood and/or bone marrow disorder, autoimmune disease or other immune disorder.
Also it may be ordered when you get a treatment that affects the WBCs to monitor your immune response condition.
3) Sample required:
A blood sample drawn from a vein in your arm or by a fingerstick (children and adults) or heelstick (infants) (see the techniques for staining blood films click here)
4) Preparation for the test:
No preparation is needed except if you take any medication that influence the WBCs count, you should tell the specialist in the lab to include this in the report
The test: principle, tools and method ===> page 2