White blood cell count

This test measures the amount of white blood cells (WBC) in blood. It is used to evaluate and manage disorders affecting the numbers of WBC. The disorders may be primary WBC disorders (directly affecting the WBC). The WBC numbers may also be affected by physical agents, toxins, or diseases which cause inflammation or suppression (decreased production) of WBC.

Laboratory tests may be done for many reasons. Tests are performed for routine health screenings or if a disease or toxicity is suspected. Lab tests may be used to determine if a medical condition is improving or worsening. Lab tests may also be used to measure the success or failure of a medication or treatment plan. Lab tests may be ordered for professional or legal reasons. You may need this test if you have:

• Acute coronary syndrome
• Bacterial meningitis
• Bird flu
• Bowel blockage
• Cancer of blood and lymph system
• Community acquired pneumonia
• Diabetes with ketoacidosis
• Diabetic hyperosmolar non-ketotic state
• Hantavirus pulmonary syndrome
• Heart artery hardening
• Heart attack
• Infection of the floor of the mouth
• Inflammation of appendix
• Inhalational anthrax
• Intestinal pouch inflammation
• Neuroleptic malignant syndrome
• Pancreatitis
• Psychotic disorder
• Sepsis syndrome
• Torsion of the ovary, ovarian pedicle or fallopian tube

Venous blood:

Before having blood collected, tell the person drawing your blood if you are allergic to latex. Tell the healthcare worker if you have a medical condition or are using a medication or supplement that causes excessive bleeding. Also tell the healthcare worker if you have felt nauseated, lightheaded, or have fainted while having blood drawn in the past.

Avoid exercising immediately before the test.

Tell the person doing the test if you are menstruating at the time of the test.

Umbilical cord blood:

Ask the healthcare worker for information about how to prepare for this test.

A sample of venous or umbilical cord blood may be collected for this test.

Venous blood:

When a blood sample from a vein is needed, a vein in your arm is usually selected. A tourniquet (large rubber strap) may be secured above the vein. The skin over the vein will be cleaned, and a needle will be inserted. You will be asked to hold very still while your blood is collected. Blood will be collected into one or more tubes, and the tourniquet will be removed. When enough blood has been collected, the healthcare worker will take the needle out.

Umbilical cord blood:

A method called percutaneous umbilical cord blood sampling may be used to collect an umbilical cord blood sample. For this method, a needle is inserted through the pregnant mother's abdomen and into the umbilical cord. Ultrasound is used to help guide the needle. Samples of the unborn baby’s umbilical cord blood are drawn out for testing. When enough blood is collected, the needle is removed.

To collect an umbilical cord blood sample after an infant is born, the healthcare worker may use a needle and syringe to draw blood from the umbilical cord while the cord is still attached to the infant. Blood samples may also be collected from the part of the umbilical cord that has been detached from the infant.

After birth, an infant's body does not need the attached umbilical cord stump or its blood vessels, but they may be used temporarily for medical purposes. If the infant has a catheter inserted in a vessel of the umbilical cord, the blood sample may be collected through the existing catheter.

The amount of discomfort you feel will depend on many factors, including your sensitivity to pain. Communicate how you are feeling with the person doing the test. Inform the person doing the test if you feel that you cannot continue with the test.

Venous blood:

During a blood draw, you may feel mild discomfort at the location where the blood sample is being collected.

Umbilical cord blood:

There are several different ways that a cord blood sample may be collected. Depending on the procedure used to obtain the sample, the test may be uncomfortable. Ask the healthcare worker to explain how the test may feel.

Venous blood:

After a blood sample is collected from your vein, a bandage, cotton ball, or gauze may be placed on the area where the needle was inserted. You may be asked to apply pressure to the area. Avoid strenuous exercise immediately after your blood draw. Contact your healthcare worker if you feel pain or see redness, swelling, or discharge from the puncture site.

Umbilical cord blood:

Depending on the procedure used to obtain a sample of cord blood, there may be special instructions for you to follow. Ask the healthcare worker for any special instructions following this procedure.

You have the right to help plan your care. To help with this plan, you must learn about your health condition and how it may be treated. You can then discuss treatment options with your caregivers. Work with them to decide what care may be used to treat you. You always have the right to refuse treatment.