newborns the range is from 10,000 to 30,000 cells per cubic millimeter. White blood cell counts are performed either manually or with automated hematology analyzers. Only the manual method will be covered in this chapter. After a brief discussion on abnormal white blood cell counts, we will cover the Unopette method for manually counting white blood cells. Abnormal White Cell Counts When white cell counts rise above normal values, the condition is referred to as leukocytosis. Leukocytosis frequently occurs when systemic or local infections (usually due to bacteria) are present. Counts for infections are highly variable. Examples of some infections and their representative white cell counts are as follows: Pneumonia—20,000 to 30,000/mm³ Meningitis—20,000 to 30,000/mm³ Appendicitis—10,000 to 30,000/mm³ D y s c r a s i a ( t h e d i s e a s e d c o n d i t i o n ) o f blood-forming tissues, such as occurs in leukemia (due to a malfunctioning of lymph and marrow tissues) also results in leukocytosis, with extremely high white cell counts. These white cell counts sometimes exceed 1,000,000/mm³. Other physiological conditions that can cause leukocytosis and a white cell count as high as 15,000/mm³ may occur as follows:  Shortly after birth  During late pregnancy  During labor  Accompanying severe pain  After exercise or meals  After cold baths  During severe emotional upset An abnormally low count, known as leukopenia, may be caused by the following conditions:  Severe or advanced bacterial infections (such as typhoid, paratyphoid, and sometimes tularemia), or when the bacterial infection has been undetected for a period of time (as with chronic beta streptococcal infections of the throat).  Infections caused by viruses and rickettsiae, such as measles, rubella, smallpox (until the 4th day), infectious hepatitis, psittacosis, dengue, tsutsugamushi fever, and influenza (when it may fall to 1,500/mm³, or shift to leukocytosis if complications develop).  Protozoal infections (such as malaria) and helminthic infections (such as trichinosis). (For example, with victims of malaria, slight leukocytosis may develop for a short time during paroxysm (the sudden intensification of symptoms). Shortly thereafter, however, leukopenia ensues.)  Overwhelming infections when the body’s defense mechanisms break down.  Anaphylactic shock  Radiation Materials Required for Unopette Procedure The Unopette method uses a disposable diluting pipette system that provides a convenient, precise, and accurate method for obtaining a white blood cell count. When the Unopette method is used, whole blood is added to a diluent. The diluent lyses (destroys) the red blood cells, but preserves the white blood cells. Once the red cells are completely lysed, the solution will be clear. The diluted blood is then added to a hemacytometer. Once the hemacytometer is loaded, the cells should be allowed to settle for 10 minutes before counting proceeds. The following materials are required to perform a white blood cell count using the Unopette method:  Disposable Unopette for WBC counts, which consists of —a shielded capillary pipette (20 microliter (Fl) capacity), and —a plastic reservoir containing a premeasured volume of diluent (1:100 dilution).  Hemacytometer and coverglass  Microscope with light source  Hand-held counter  Laboratory chit 7-17