Total leukocyte count (TLC)

Introduction:

The TLC blood test is one of the most common blood test ordered by doctors, and TLC stands for ‘Total Leukocyte Count’. Leukocytes are white blood cells which are important components of the blood. The main role of white blood cells or leukocytes is to fight infection and keep the body healthy. Leukocytes are essential for the overall well-being of the body.

The WBCs account only for 1% of your blood, but they have a significant effect on the healthiness of your body. There are 5 types of WBCs, each with a different function. Below are the types of WBCs and their functions:

Lymphocytes: These cells produce antibodies to help the body defend itself against bacteria, viruses, and other possible threats.
Neutrophils: These are powerful leukocytes that fight and destroy bacteria and fungi.
Basophils: These white blood cells mostly help the body combat allergies, and they alert the body to infections by secreting certain chemicals into the bloodstream.
Eosinophils: These white blood cells too are involved in the body’s response to allergy and are responsible for destroying cancer cells and parasites.
Monocytes: These are another set of potent white blood cells that attack and break down germs or bacteria that enter the body. These cells migrate to the organs such as the spleen, liver, lungs and the bone marrow, whichever is under attack of the harmful invading foreign bodies, and destroy them. Monocytes also help remove dead or damaged tissue and destroy cancer cells.

The average lifespan of a leukocyte is 13 to 20 days, and their lifespan in the peripheral blood is only 7 to 10 hours after they migrate from the bone marrow into the bloodstream. This is the reason why a healthy body produces around 100 billion leukocytes per day to replace the perished leukocytes.

The TLC blood test forms a part of the complete blood test which determines other values such as complete blood count (CBC), platelet count, red blood cells count (RBC), and hemoglobin percentage. A DLC test may be ordered along with a TLC test. DLC stands for Differential Leukocyte Count and is done to measure the percentage of each type of white blood cell or leukocyte in the body.

The parameters include counts of lymphocytes, neutrophils, eosinophils, monocytes, and basophils.

What is a TLC Blood Test?

TLC test means the test is done to determine the number of white blood cells in the blood. The WBC count helps determine the body’s capacity to fight diseases.

The normal range for TLC is considered to be between 4000 to 11000 cells/cubic millimeter of blood. A decrease in the TLC count is referred to as leukopenia, and it will cause a decline in the body’s ability to fight diseases. An increase in the TLC count is known as leukocytosis, and it is a condition in which the body produces more WBCs than normal. Leukocytosis is common among people who have an acute infection or illness and in newborn infants.

How is this test performed?

Requiremens:

Principle using hemocytometer:

A very large number of WBC or leukocytes are present in the blood specimen. So, the leukocytes are counted by using a special type of chamber, designed for the counting of blood cells in the specimen, known as Hemocytometer or Neubauer’s chamber.

For this, the blood specimen is diluted (usually in ration 1:20) with the help of WBC diluting fluid which preserve, stains and fix the WBCs and lysis the red blood cells.

After diluting the specimen, the content is charged on hemocytometer/Neubauer’s chamber in the areas specific for WBC count.

The composition of WBC diluting fluid (Turk’s fluid)

Components	Quantity
Glacial acetic acid	2 ml
Gentian violet (1%aqueos)	1 ml
NaCl	0.9 gram
Distilled water	97ml

The final pH of the solution (at 25 degree Celsius) varies from 2.0 – 2.4 which depends on the composition and companies who manufacture it.

Hemocytometer/Neubauer’s chamber:

This is a special type of glass chamber that is used for the cell counting, especially for blood cells. The chamber has ruled the area of total 9 square mm and the septh is 0.1mm as when the coverslip is placed on the surface of the counting chamber, the space between the bottom of the cover glass and the base of grooved area measures 0.1 mm in depth.

Out of 9 squares, the 4 corner squares are used for the white blood cell count. Every large corner square is further divided into the 16 small squares, so the total no. of the area to be counted for WBC count-

R – RBC AREAS; W – WBC AREAS.

16 *4 =64 small squares of the 4 large corner squares

Counting the white blood cells under microscope:

Focus the ruling using the 10* objective lens and then count the WBCs in 4 large corner squares using 40* objective lens.

Count the cells which are lying on right and lower lines of the 4 corner squared but not the opposite line. In case of marginal cells, count the cells on “L” line that is either on right and lower lines or left or upper lines.

Calculations for the total WBC count using hemocytometer:

After counting the cells under the microscope, we know the no. of WBC in 4 corner squares. Lets consider it as “N” no. of cells.
Now. The volume of the fluid inside the chamber is the product of area and depth of the hemocytometer.
The depth of the hemocytometer is 0.1 or 1/10 mm
Now apply the following formula to get the total WBC count-

Thus, 2/5 mm³ contains = N * dilution

Then, 1 mm³contains = N * 50 /mm³

Using the Above formula we can calculate the Total No. of White Blood Cells present in the Blood Specimen.

NORMAL VALUES OF WHITE BLOOD CELLS

According to the Mayo Clinic, these are the normal ranges of WBCs per microlitre (or mm³) of blood by age:

AGE OF PERSON	WBCs / Cu-mm OF BLOOD
immediately after birth	9,000 to 30,000
1 to 7 days	9,400 to 34,000
8 to 14 days	5,000 to 21,000
15 days to 1 month	5,000 to 20,000
2 to 5 months	5,000 to 15,000
6 months to 1 year	6,000 to 11,000
2 years	5,000 to 12,000
3 to 5 years	4,000 to 12,000
6 to 11 years	3,400 to 10,000
12 to 15 years	3,500 to 9,000
Adults	3,500 to 10,500

The normal percentages of the types of WBCs in overall Leucocyte count are usually in these ranges:

TYPE OF WBC	NORMAL PERCENTAGE IN BLOOD
Neutrophil	45% to 75%
Eosinophil	2% to 6%
Basophil	0% to 1%
Monocytes	2% to 10%
Lymphocytes	20% to 40%

Is there any risk associated with this test?

There is no risk associated with the test. However, since this test involves a needle prick to withdraw the blood sample, in very rare cases, a patient may experience increased bleeding, hematoma formation (blood collection under the skin), bruising or infection at the site of needle prick.

Why is TLC done?

The Total Leukocyte Count Test is performed:

As a part of Complete Blood Count (CBC) Test in regular health checkups
- To help diagnose infections and inflammation
- To help diagnose conditions that decrease WBC count like bone marrow disorders
- To monitor bone marrow function
- To monitor chemotherapy treatment
- Differentiate between an acute and chronic infection
- Identify an allergic reaction in the body
- Diagnose certain types of cancer, especially blood cancer such as leukemia or lymphoma

Interpreting TLC results

Interpretations

Normal range (Approx.):

· Newborns: 9,000 to 30,000/mm3

· Children below 2 years age: 6,200 to 17,000/ mm3

· Children over 2 years age and adults: 5,000 to 10,000/ mm3

Note: Normal range of leukocyte count depends on a number of factors apart from age, including gender, health condition, previous instance of diseases, vaccinations, etc. The range also varies slightly between different laboratories performing the test.

Higher than the normal leukocyte count indicates an infection or inflammation being treated by the body.

Lower than the normal leukocyte count indicates improper functioning of the immune system.

TLC Normal Range For Adults

The normal reference range for adults (males and females) is as follows:

Total leukocytes: 4.00-11.0 x 10 9/L
Neutrophils: 2.5–7.5 x 10 9/L
Lymphocytes: 1.5–3.5 x 10 9/L
Monocytes: 0.2–0.8 x 10 9/L
Eosinophils: 0.04-0.4 x 10 9/L
Basophils: 0.01-0.1 x 10 9/L

What are the Causes of High TLC Count?

If the results of a TLC blood test show an increase in the number of WBCs, i.e., if the TLC count high when more than 11000 cells/ cubic millimeter of blood, the condition is called Leukocytosis. Leukocytosis may be caused by a number of reasons such as:

Allergy or a severe allergic reaction in the body
Cancer such as chronic lymphocytic leukemia or chronic myelogenous leukemia
Bacterial or viral infections
Rheumatoid arthritis
Immunosuppression caused by diseases like HIV
Inflammation caused by conditions such as rheumatoid arthritis
Injury
Severe physical or emotional stress
Injury
Pregnancy or labor
Smoking
Respiratory illnesses such as whooping cough or tuberculosis
Regular use of drugs such as corticosteroids and epinephrine

What are the Causes of Low TLC Count?

If the results of a TLC test show the WBC count to be less than 4000 cells/ cubic millimeter of blood. This condition is referred to as leukopenia, and it may be caused by:

Viral infections that temporarily disrupt the production of white blood cell production in the bone marrow
Certain congenital disorders that are responsible for weakened bone marrow function
Diseases that damage the bone marrow
Autoimmune disorders such as lupus that cause the destruction of the white blood cells or the bone marrow
Medications such as antibiotics that destroy white blood cells
Sarcoidosis
Aplastic anemia
Chemotherapy or radiation therapy
Tuberculosis
Rheumatoid arthritis
Infections such as malaria, dengue, and typhoid
Malnutrition and vitamin deficiencies

How to Reduce TLC in Blood?

If you are detected with high TLC in blood, there are not many options to help reduce the high TLC. However, aiming to reduce the amount of calorie intake in a day and maintaining a healthy body weight may help reduce the high TLC. Other steps you may take to maintain a normal TLC include:

Keeping the intake of saturated fat below 7% of your total calorie intake in a day
Lowering the daily intake of cholesterol to less than 200 milligrams
Limiting your sodium intake to 2400 milligrams a day
Increasing your physical activity and exercising for a minimum of 30 minutes for 5 days a week
Consuming fresh fruits and vegetables and increasing your intake of soluble fiber.

How to Increase TLC in Blood?

If your TLC blood test values are lowered, you can work to increase the levels by:

Including zinc in your diet
Increasing your folic acid intake through supplements or foods rich in folic acid
Including yogurt and selenium sources in your daily food
Consuming green tea, as it is rich in antioxidants which supports the immune system and encourages WBC production
Making fatty fish such as mackerel and salmon, which are rich in omega-3 fatty acids, a regular part of your diet.