GLOSSARY OF TERMS

The proportion of the blood occupied by the red cells. Normal values are 40 to 54 per cent in males and 35 to 47 per cent in females. If the haematocrit is below normal, the condition is called “anaemia.” If the haematocrit is above normal, the condition is called “erythrocytosis.”


A medical doctor who specialises in the treatment of blood cell diseases..

A type of pathologist who studies diseases of blood cells by looking at peripheral blood smears, bone marrow aspirates and biopsies, and lymph nodes and other tissues. The haematopathologist uses his or her expertise to identify diseases such as blood cancers. In addition to using a microscope, a haematopathologist also uses laboratory values, flow cytometry and molecular diagnostic tests to make the most accurate diagnosis. The haematopathologist works closely with the haematologist/oncologist who sees the patient and decides on the best treatment based upon the diagnosis.


The process of blood cell development in the marrow. The most undeveloped cells in the marrow are stem cells. They start the process of blood cell development. The stem cells begin to develop into young or immature blood cells such as red cells or white cells of various types. This process is called “differentiation.”
The young or immature blood cells then further develop into fully functional blood cells. This process is called “maturation.” The mature cells leave the marrow, enter the blood and circulate throughout the body. Haematopoiesis is a continuous process that is active normally throughout life. The reason for this activity is that most blood cells live for short periods and must be continually replaced. Red cells live for months, platelets live for a week or two, and white cells live for a few days. About 500 billion blood cells are made each day. When the marrow is invaded with cancer cells, it cannot produce enough normal blood cells to meet the constant demand for them, and the numbers in the blood cell counts become severely depleted.


The iron-containing pigment in red cells that carries oxygen to the tissue cells. A reduction in the number of red cells decreases the amount of haemoglobin in the blood. A decreased blood haemoglobin concentration is called “anaemia.” A low haemoglobin concentration decreases the oxygen-carrying capacity of blood. If severe, this decreased capacity may limit a person’s ability to exert him or herself. Normal values of blood haemoglobin are 12 to 16 grams per decilitre (g/dL). Compared to men, healthy women have, on average, about 10 per cent less haemoglobin in their blood.


The abbreviation for human leukocyte antigen(s). These are proteins on the surface of most tissue cells, and they give an individual his or her unique tissue type. HLA factors are inherited from mother and father, and the greatest chance of having the same HLA type is between siblings. On average, one in four siblings is expected to share the same HLA type. The testing for HLA factors is referred to as “tissue typing.” There are six major groups of HLA: A, B, C, D, Dr, and Dq. These proteins on the surface of cells act as antigens when donated (transplanted) to another individual, the recipient. If the antigens on the donor cells are identical (as in identical twins) or very similar (as in HLA-matched siblings), the transplant Acute Myeloid Leukaemia (donated stem cells) is more likely to survive (engraft) in the recipient. In addition, the recipient’s body cells are less likely to be attacked by the donated immune cells (a result called “graft-versus-host disease”).