White blood cell count is one of the indices found on a blood test called a complete blood cell count. Doctors will order a CBC as part of routine or basic lab work. The total WBC count for adults is generally between 5,000 to 10,000/mm3. When adult values exceed 10,000 WBCs doctors will call this "leukocytosis." There are five major types of WBCs and each type has a different role in the body.
Infection
Infection is the most common cause of an elevated WBC count. The types of WBCs that rise because of infection are lymphocytes, monocytes and neutrophils. Infection causes the body to mount an immune response by releasing WBCs. Without adequate WBC production, a person's body cannot adequately fight off a pathogen. In an acute infection, neutrophils respond right away and then quickly decrease. The WBC count should return to normal within days after the person's symptoms have subsided. In a chronic infection, WBC counts may remain elevated for the duration of the illness and may continually increase as the infection worsens.
Inflammation
Inflammation can result from a sprained ankle or from chronic disease. Essentially, the body creates extra WBCs as a response to tissue damage. When tissue is damaged, a portion of it dies, which doctors call necrosis, and the WBCs are responsible for cleaning up the area and carrying away the dead tissue.
Cancer
Cancer can cause the WBC count to increase in a couple of ways. In cancers like leukemia, known as myeloproliferative disorders, the bone marrow produces excess WBCs and releases them into the bloodstream. This causes a drastic increase in WBCs. Cancers that do not involve the marrow may also cause an increase in WBCs. One example would be advanced lung cancer, which causes a rise in WBCs via an unknown mechanism.
Other Causes
Dehydration stresses the body and causes an increase in WBC count. Dehydration also causes the blood to become more concentrated which can result in the appearance of WBC elevation on a blood test.
Certain medications can also cause an increase in WBC count. Drugs that may cause increased WBC levels include adrenaline, allpurinol, aspirin, chloroform, epinephrine, heparin, quinine, steroids, and triamterene.
Parasitic infestation can stimulate the production of WBCs, particularly basophils and eosinophols. An allergic response may cause these same types of WBCs to increase. As the allergic response decreases, so should the WBC count.
Lastly, severe thyroid hormone imbalance, known as "thyroid storm" may lead to an elevation of WBCs.
References
- "Mosby's Manual of Diagnostics and Laboratory Tests"; 3rd Ed; Pagano; 2006
- "Henry's Clinical Diagnosis and Management by Laboratory Methods"; 21st Ed; McPherson & Pincus; 2006
