Examination of white blood cells

White blood cells count 

White blood cells  counts are performed by automated cell counters on blood samples appropriately  diluted with a solution that lyses the erythrocytes(e.g., an acid or a detergent), but preserves  white blood cells integrity. Manual counting of white blood cells is used only when the instrument reports a  potential interference or the count is beyond instrument linearity limits. Manual counts are subject to much greater technical variation than automated counts because of technical and statistical factors. 

False white blood cells counts

Automated white blood cells counts may be falsely elevated as a result of cryoglobulins or  cryofibrinogen,  clumped platelets or fibrin from an inadequately anticoagulated or mixed sample, ethylenediaminetetraacetic acid (EDTA)-induced platelet aggregation, nucleated red  blood cells, or nonlysed red cells, and falsely decreased because of EDTA-induced neutrophil  aggregation. This potential interference is very instrument dependent, and current analyzers use a variety of algorithms to minimize their effect and flag those rare samples in which accurate  automated analysis cannot be performed. With respect to nucleated red cells, high end analyzers routinely and accurately quantify these cells with detection limits of 1 to 2 nucleated red  cells per 100 white blood cells.  Nucleated red cells are normally present in small numbers in neonatal blood, and are increased in a variety of hematopoietic disorders and conditions of severe hematopoietic stress.

White blood cells differential

white blood cells  in the blood serve different functions and arise from different hematopoietic lineages, so it is important to evaluate each of the major white blood cells  types separately. Modern automated instruments use multiple parameters to identify and enumerate the five major morphologic white blood cells  types in blood: neutrophils, basophils, eosinophils, lymphocytes, and monocytes, as well as indicate the possible presence of immature or abnormal forms. 

Normal white blood cells variation

The normal differential white blood cells  count varies with age. polymorphonuclear neutrophils are predominant in the first few days after birth, but thereafter  lymphocytes account for the majority of leukocytes.This pattern persists up to approximately 4  to 5 years of age, when the polymorphonuclear leukocyte again becomes the predominant cell  and remains so throughout the rest of childhood and adult life. Chapter 8 discusses the leukocyte count in older persons. The leukocyte count may decrease slightly in older subjects be-cause of a fall in the lymphocyte count with age. The reference range for neutrophil counts is  lower in Americans of African descent, and in African, Afro-Caribbean, and some Middle Eastern populations than in persons of European descent.