The blood cell count is often examined in routine clinical praxis. Physiologic leucocyte count is in range 4-10 × 109 in liter of blood. Abnormal values of leukocytes and subtypes of leukocytes in differential count are often present. Changes in leukocytes counts are caused by variety of benignant or malignant conditions. It is important in clinical praxis to interpret changes in blood cell count correctly and choose adequate approach in investigation process. In general, leukocytosis and leukocytopenia may present in primary hematologic disorder or secondary/reactive states, caused by reaction of hematopoiesis to underlying condition. This article review common causes of leukocytosis or leucopenia and give basic advice how to investigate patients with changes in leukocytes count.
Keywords: differential blood cell count; leucopenia; leukaemia; leukemia; leukocytosis; leukopenia.