WBC Count Test

WBC or White Blood Cells are cells of immune system that are formed from the hematopoietic stem cells of the bone marrow. White blood cellsare also known as Leukocytes. The main functions of White blood cells  are to protect the body from infectious organism and foreign particles. White blood cells can be of five different types. The names are, neutrophils, eosinophils, basophils, lymphocytes and monocytes.



A White blood cell count is a blood test used to determine the concentration of white blood cells in a patient’s blood. There are two types of white blood cell count tests. They are

  • TLC or Total Leukocyte Count: TLC is used to measure the total number of white blood cells in a patient’s blood.
  • DLC or Differential Leukocyte Count: The differential leukocyte count is used to measure the percentage of each of the five types of white blood cells i.e., lymphocytes, neutrophils, basophils, monocytes and eosinophils.

Alternative Names

Alternative names of WBC count are White Blood Cell Count and Leukocyte Count.

Description of the Test

The white blood cell count tests are usually done either with the help of automated counting instruments or through manual method using microscope and counting chamber. The differential leukocyte count can be carried out in automated method using an electronic cell counter or with the aid of an image analysis instrument. In some case, the white blood cell count may give an abnormal report or some of the cell population might appear as flagged. This shows that one or more of the results are atypical. In such case, the test will be repeated manually.

The manual method for measuring the white blood cell concentration is usually done in case when the automated counting instrument shows very low result or in case where the patient has any condition that might interfere with the automated counting technique.

In manual WBC differential count, a thin smear of the blood is prepared on a clean dry glass slide which is then stained and observed under microscope. The leukocytes are differentiated based on their size, shape, color, presence or absence of granules, shape of the lobules and so on.

 Apart from this, the following procedures are carried out as apart of the differential count:

  • Detailed study on the RBC morphology is carried out. This includes determining the size and shape of RBC, detecting the presence of any abnormal and immature type of RBC’s, determining the number of nucleated RBCs per 100 WBCs.
  • An estimate of white blood cell count and platelet count is carried out and compared with that the result obtained through automated WBC count.

Purpose of theTest

The white blood cell count test is usually done either as a part of general health check up or to detect a variety of illness. The WBC count test helps the physician in investigating variety of illness and it also helps in monitoring the patient’s recovery from illness. A high level of WBC count is usually observed in case of infection and inflammation. The WBC count may also appear to be elevated in patients with leukemia, allergy, tissue injury and systemic illness. A low level of WBC count is usually observed in patients suffering from certain viral infections and in immunodeficiency states. The WBC count may also appear to be decreased in case of bone marrow failure. On further test, a patient with elevated WBC count is found to be returning to a normal WBC count level, this indicates the patient is in recovery stage. On the other hand if an abnormal WBC count is found to be worsening even more, this shows that the patient’s health condition too is worsening.


Even though no special precautions are needed, it is necessary that you should inform the physician about any medication you are under going. This is because some medications may interfere with the WBC count test result.

Certain drugs may result in giving a false WBC count result either by increasing the patient’s WBC count level or by decreasing the patient’s WBC count level. Allopurinol, heparin, aspirin, quinine, epinephrine, chloroform, corticosteroids and triamterene are the drugs that may increase the white blood cell count level; drugs such as antibiotics, anticonvulsants, arsenicals, diuretics, sulfonamides, antihistamines, anti thyroid medicines, chemotherapy drugs and barbiturates on the other hand may cause a decrease in the white blood cell count level.

Normal Results

The normal values of WBC count may vary with the age. The WBC count is usually higher in children under one years of age and may gradually decrease towards the adulthood. The normalwhite blood cell counts in adults are as follows:

TLC or Total Leukocyte Count – 4,000 – 11,000 / µl
DLC or Differential Leukocyte Count

  • Neutrophils-      40- 70 %
  • Lymphocytes-   20 - 40 %
  • Eosinophils-        1 – 6 %
  • Monocytes-       2 – 10 %
  • Basophils-           0 - 2 %

Abnormal Results

Any deviation from the above normal result may indicate that the patient is suffering from some infection or some illness.

  • Leukopenia or low level of white blood cell count is usually observed in patients undergoing radiation and chemotherapy, patients suffering from collagen-vascular disease, individuals with abnormalities in spleen, liver function, bone marrow failure etc.
  • Leukocytosis or elevated white blood cell count is usually observed in anemic patients, patients suffering from certain inflammatory diseases like allergy and rheumatoid arthritis, in case of infectious diseases, patients suffering from leukemia etc.