Blood count

(Total) blood count (BC) is a routine screening test. It is performed at each admission to the hospital, as well as when a hematological or more serious infectious disease is suspected.

BC components:
 * Leukocytes (Leu, WBC) + so-called differential, i.e. percentage of lymphocyte, monocyte, neutrophils, basophils, and eosinophilic granulocytes.
 * Erythrocytes (Ery, RBC).
 * Erythrocyte parameters, i.e. their volume (MCV), hemoglobin content in the cell (MCH), its concentration in the cell (MCHC), erythrocyte volume distribution width (RDW).
 * Content of hemoglobin u per blood volume (Hb) and hematocrit (Hct).
 * Thrombocytes (Tr, PLT).

Procedure and methods used
Venous blood is collected in a tube with EDTA. The numbers and relative proportions of the individual cell lines are analyzed using flow cytometry. Flow cytometry determines not only the number of cells of each cell type per unit volume but also the volumes of a given type. Some abnormal cells may be inaccurately identified (schistocytes, immature and leukemic forms of leukocytes). In case of suspicion of the presence of abnormal cell types, evaluation under a microscope by an experienced laboratory worker (so-called "manual" differential) is necessary. Hb concentration is determined using colorimetry (= absorption spectrometry). Hct is determined after centrifugation of the sample as the ratio (percentage) of the condensed ("crushed") volume of cell elements (Ery + Leu + Tr) to the total volume. Erythrocyte parameters (MCV, MCH, MCHC) are calculated using simple equations.

Physiological values


Reticulocytes: 0,5–1,5%


 * It reflects the dynamics of changes in the number of erythrocytes. Decreased values ​​usually indicate anemia from underproduction, while increased values ​​indicate anemia from increased losses.

MCV (mean corpuscular volume, mean erythrocyte volume),

MCH (mean corpuscular hemoglobin, the average amount of Hb in the cell),
 * divides anemia into microcytic, normocytic, and macrocytic.


 * divides anemia into hypochromic and normochromic.

MCHC (mean corpuscular hemoglobin concentration, mean concentration of Hb in erythrocytes).

RDW (erythrocyte distribution width): 11,5–14,5%,


 * provides an overview of variability in red blood cell size (anisocytosis).

Leu: 4000–10&thinsp;000/µl (children about 25% more, toddlers – about 50% more)

Leukocyte differential count
 * Neutrophils: 30-85% (children less);
 * Lymphocyte: 15–50% In absolute number: 1500–40&thinsp;00/µl (children more, up to 10,000);''
 * Monocyte: 1–12%;
 * Eosinophils: 3 ± 3%;
 * Basophils: 1 ± 1%.

Thrombocytes: [tel:150&#x20;000–350 150 000–350]&thinsp;000/µl

Physiological changes in blood count and in differential calculus in childhood
Normal levels of red and white blood cells in the peripheral blood in children vary with age.

In the perinatal period, hemoglobin (Hb) is composed of 80% fetal hemoglobin (HbF – chains α2 γ2) and 20% adult hemoglobin (HbA1 – chains α2 β2). After birth, fetal hemoglobin is exchanged for adult hemoglobin within 6-12 months. In the first days after birth, short-term polyglobulia (relative polycythemia) with a hemoglobin concentration of about 195 g/l due to a reduction in blood volume, an increased reticulocyte count to 3% and erythrocyte macrocytosis is present. After the neonatal period, there is a steady decrease in hemoglobin levels due to attenuated erythropoiesis. At the age of 10 weeks, the lowest hemoglobin level is reached (up to 95 g/l, on average 115 g/l) – a phenomenon sometimes called "three-month anemia". This is followed by a steady increase until the adult values ​​reach puberty. The normal value of reticulocytes is around 1% and the lifespan of the erythrocyte in the blood is 120 days. In premature infants, the decrease in hemoglobin is more pronounced due to insufficient production of erythropoietin – "premature anemia". The decrease in Hb is compensated by shifting the oxygen dissociation curve to the right and easier delivery of oxygen to the tissues. The volume of erythrocytes also changes. After birth it is 119 fl (macrocytosis), then decreases to 70-77 fl at 6 months and gradually rises to 80-90 fl in adulthood.
 * Hemoglobin:
 * Erythrocytes:


 * Leukocytes

The number of leukocytes rises sharply during the first days of life to values around 20×109/l (leukocytosis formed by granulocytes – neutrophils, eosinophils, and basophils) – neutrophils with a shift to the left. After about one week, the number of leukocytes decreases again ("first crossing" on day 5) and the predominance of lymphocytes (relative lymphocytosis) occurs by the age of 4, then the neutrophil/lymphocyte ratio equalizes and later granulocytes predominate until old age ("second crossing" in the 5th year). Monocytes make up 5-10% of the cells in the differential budget.


 * Platelets

The normal number is 140-400 × 109/l regardless of age, volume 7-11 fl and their life in the circulation 7-10 days.

=References=

Related Articles

 * Blood
 * Blood plasma
 * Blood samples for examination
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 * Biochemical analysis of blood ▪ Laboratory examination of acid-base balance
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 * Physiological values of blood elements