IMPORTANCE OF HAEMATOLOGICAL PARAMETERS
Haematological assays seldom provide an etiological diagnosis but they remain, nevertheless indispensable diagnostic tools to evaluate health and disease conditions in patients for monitoring the response and progress of patients to therapeutic regime and to offer prognosis. The routine collection and processing of blood samples allows the evaluation of haematological responses to diseases (Howlett and Jaime, 2008).
The full blood count sometimes referred to as a full blood examination or complete blood count is one of the most commonly performed blood tests, as it can tell us so much about the status of our health. It is important for diagnosing conditions in which the number of blood cells abnormally high or abnormally low or the cells themselves are abnormal (Fleming and De silva, 2008).
A full haematology (complete blood count) measures the status of a number of different features of the blood including:
• The number of haemoglobin in the blood
• The number of red blood cells (red cell count)
• The % of the blood cells as proportion of parked cell volume (PCV)
• The volume of red blood cells (mean cell volume, MCV)
• The average amount of haemoglobin in the red blood cells (mean cell haemoglobin, MCH)
• The number of white blood cells (white cell count)
• Leucocyte differential count (percentage of the different types of WBC), and
• The number of platelets. (Owoyele et al., 2013)
2.8.1 RED BLOOD COUNT (RBC)
Red blood cells are an erythrocyte which specializes in transportation of oxygen to the presence of haemoglobin with the erythrocytes which also contributes to the red colouration of blood. Red cell count is the estimation of the number of red blood cells per litre of blood. Low red blood counts may indicate anaemia as a result of blood loss, bone marrow failure and malnutrition such as iron deficiency, over hydration, or mechanical damage to red blood cells (Aiello, 1998).
Red blood cell count shows the number of red cell an individual has in its blood. The function of red blood cell is to carry oxygen to the tissue at pressures sufficient to permit rapid diffusion of oxygen. This is done by the help of a carrier molecular haemoglobin. Interference with synthesis or release of haemoglobin, production or survival of red blood cells or metabolism causes disease (Aiello, 1998).
Red blood cells form the main cellular component of the blood that is about 45% of total blood volume in an adult. It is this component of the blood that gives the blood its red colour. Each litre of blood contains 5×1012 red cells, the exact number varying with age, gender and state of health. Tissue hypoxia leads to the release of the hormone Erythropoietin which stimulates progenitor cells to develop into pronormoblasts (proerythroblasts) (Fleming et al., 2008).
The disorders of red blood cells are;
• Anaemia
• Haemoglobinopathy
• Disorders due to red cell enzymes defects eg G6PD deficiency.
• Disorders due to red cell membrane defects e.g hereditary spherocytosis.
• Polycythaemias (Fleming et al., 2008).
2.8.1.1 Anaemia:
This is a red blood cell deficiency disease, which result from a decrease in the amount of haemoglobin in the red blood cells. As there is reduced haemoglobin, there is subsequent decrease in the level of oxygen transported by the blood; as haemoglobin functions to transport oxygen through the red blood cells to different parts of the body (Krinke, 2000).
There are three main types of anaemia;
• That due to blood loss,
• That due to decreased red blood cell production, and
• That due to increased red blood cell breakdown (Krinke, 2000).
The common symptoms of anaemia due to reduced amount of oxygen in the body include;
• Tiredness or weariness,
• Having little energy (lethargy),
• Feeling faint, and
• Becoming easily breathless or shortness of breath (Berridge, 2012).
Because iron is the precursor for the production of haemoglobin, lack of iron is the most common cause of anaemia. Other causes may include; bone marrow problems, lack of folic acid and vitamin B12, and red blood cells problems (Ben-ami et al., 2011).
Anaemia can also be classified based on the size of red blood cell and haemoglobin of each cell. If the cells are small the anaemia caused is called microcytic anaemia. If the cells are large, the type of anaemia caused is called macrocytic anaemia, when the cells are normally sized it is called normacytic anaemia. Diagnosis in men is based on a haemoglobin of less than 130 to 140g/L (13 to 14g/dL), while in women it must be less than 120 to 130g/L (12 to 13g/dL) (Ben-ami et al., 2011).
2.8.1.2 Haemoglobinopathy:
This is a type of disorder that results in abnormal structure of one of the globins of the haemoglobin molecules. It is in the globin molecule that the defect is seen. Haemoglobinopathy can cause red blood disorder, since the globin proteins in the haemoglobin molecule are structurally deformed (Weatherall and Clegg, 2001).
Haemoglobinopathies are inherited conditions, caused by changes in the genes that code for parts of the haemoglobin molecules of the red blood cells; which carries oxygen in the blood. People with haemoglobinopathies make insufficient and/or abnormal haemoglobin (example, thalassaemia and sickle cell disease), which can cause a wide variety of problems. Haemoglobinopathy patients often require regular blood transfusions which can lead to iron overload if not monitored and treated (Warrel et al., 2005).
2.8.1.3 Disorders due to red cell enzyme defect
The red cell enzymes are enzymes which catalyses the production and function of red blood cells. These enzymes include: ATPases, anion transport protein, glyceraldehyde 3-phosphate dehydrogenase, protein kinases, adenylate cyclase, and acetylcholinesterase. Most of them are tightly bound to the membrane and are present in small amount (Warrel et al., 2005).
When these enzymes are deficient, there are possible effects on the productions, structures and functions of red blood cells. For example, pyruvate kinase deficiency affects the survival of red blood cells and causes deformity on them into echinocytes (“burr cells”) on peripheral blood smears. Also, glucose-6-phosphate dehydrogenase deficiency also imposes disorder to the red blood cells in a way of hemolysis (spontaneous destruction of red blood cells) and resultant jaundice in response to a number of triggers, such as certain foods, illness or medications (Frank, 2005).
There is no known treatment for these disorders caused by deficiency in these enzymes, other than avoiding known triggers (Frank, 2005).
2.8.1.4 Disorders due to red cell membrane defects
Red cell membrane disorders are inherited disorders due to mutations in various membrane or skeletal proteins, resulting in increased red cell deformability, reduced life span and premature removal of the erythrocytes from the circulation. The red cell membrane disorders include hereditary spherocytosis, hereditary elliptocytosis, hereditary pyropoikilocytosis, and hereditary stomatocytosis (Maxwel, 2010). These comprise an important group of inherited haemolytic anaemias. For instance hereditary spherocytosis which is the most common congenital haemolytic anaemia, is an autosomal dominant abnormality caused by mutations in the shape of erythrocytes, where the abnormal erythrocytes are sphere-shaped rather than the normal biconcave disk shaped. As a result of this change in shape, there is interference in the cell’s ability to be flexible to travel from the arteries to the smaller capillaries. This difference in shape also makes the red blood cells more prone to rupture (Maxwel, 2010).
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