Full Blood Count Interpretation
Red Blood Cells
Haemoglobin:
Haemoglobin is the oxygen carrying protein found in the blood and its concentration can be measured. The normal range for haemoglobin differs between men and women. For men the normal range is 130-180g/L and for women the range is 120-160g/L. when the haemoglobin concentrations fall below the respective ranges, it is known as anaemia. There are several causes of anaemia (a comprehensive summary is found in our Introduction to Anaemias page). An excess in haemoglobin or red cell mass is known as erythrocytosis (or polycythaemia). Erythrocytosis can either be spurious ("apparent") or true. Spurious erythrocytosis occurs when there is reduction in plasma volume. Example causes of this include diuretic use and severe dehydration. A reduction plasma will make the red cell mass/haematocrit look more than it is - see Figure 1.
Figure 1: Normal whole blood is made of 55% plasma. When plasma volume reduces, it appears the red cell mass or haematocrit is greater than it actually is.
True causes of erythrocytosis can be categorized into either primary or secondary. Primary means a problem within the bone marrow itself. This is called polycythaemia vera and is due to a JAK2 mutation in bone marrow stem cells, which consequently increases proliferation of red cells and other myeloid cells (platelets, basophils, eosinophils). Secondary refers to reactive causes of increased red cell production. In chronic hypoxaemia, for example in chronic smokers, COPD, cyanotic heart disease, the body responds by increasing red cell production to increase the amount of oxygen carried in the blood. Other secondary causes include tumors which produce EPO (the growth factor responsible for red blood cell production). See Figure 2 for a summary of the approach to polycythaemia.
Figure 2: Approach to erythrocytosis (polycythaemia)
Mean Cell volume (MCV):
The mean cell volume is used to describe the mean volume of the red blood cells found in the blood. The normal MCV range is 76-96fL. MCV is used to classify the type of anaemia; a low MCV causes a microcytic anaemia, a normal MCV is seen in normocytic anaemia and a high MCV causes a macrocytic anaemia.
Mean Corpuscular Haemoglobin concentration (MCHC):
The MHCH is used to describe the mean concentration of haemoglobin in each red blood cell. The MHCH may be reduced or increased in disease states but occurs very late in the disease progression. The normal range for both males and females is 320-360g/L.
White Blood Cells
Neutrophils:
Neutrophils are the most common subtype of granulocytes. They contain toxic enzymes and are the main cell type that help fight against bacterial infections. The normal range for neutrophils is 2.0-7.5 x 10^9/L.
When the neutrophil count falls below this range it is known as neutropenia. The most common cause of neutropenia is post-chemotherapy, as this impairs the bone marrow's ability to produce neutrophils. Neutropenia can also be caused by leukaemia and congenital diseases. A high neutrophil count is known as neutrophilia and the most common cause of neutrophilia is bacterial infections. It can also be seen in inflammatory diseases such as rheumatoid arthritis.
Lymphocytes:
Lymphocytes are further divided into T cells and B cells. They are largely involved in the immune system's fight against viruses and help make up the immune system's memory. The normal range for lymphocytes is 1.0-4.5 x 10^9/L.
A low lymphocyte count is known as lymphocytopenia and the most common cause is viral infections. A high lymphocyte count is called lymphocytosis and it is also most commonly caused by viral/bacterial infections. Lymphocytosis can also be caused by malignant processes such as leukaemia and lymphoma.
Eosinophils:
The normal range for eosinophils is 0.04-0.4 x 10^9/L. A high eosinophil count is known as eosinophilia and is commonly caused by allergy, drug reactions and infection by parasites.
Basophils:
The normal range for basophils is 0.0-0.1 x 10^9/L. a high basophil count is known as basophilia and is commonly seen in leukaemias and lymphomas and also inflammatory conditions.
Platelets:
The normal platelet count is 150-450 x 10^9/L. A high platelet count is known as thrombocytosis and it is commonly seen in primary haematological diseases such as essential thrombocythemia. The platelet count may increase secondary to iron deficiency anaemia (as the body thinks there is bleeding and therefore increases the platelet count), inflammatory or malignant processes in the body - this is called Reactive thrombocytosis. A low platelet count is known as thrombocytopenia - causes can be categorized into failure of production, peripheral destruction, sequestration, and increased consumption.
Pancytopenia:
Pancytopenia describes a decreased amount of all cell lines (low red blood cells, low white cells and low platelets) in the peripheral blood. Causes of pancytopenia can be either due to impaired production in the bone marrow, or peripheral destruction of cells, or both. Causes of impaired production by the bone marrow include malignancies of the bone marrow such as leukemia, myelodysplasia, myelofibrosis, aplastic anaemia, and infiltration of the marrow by sarcoidosis. Infections can also infect precursor cells of the bone marrow and impair production of haematopoietic cells. Examples of viruses that can cause pancytopenia include Hepatitis viruses, EBV, Parvovirus, and HIV. Systemic lupus erythematosus can cause pancytopenia due to production of antibodies which attack all 3 lines of cell types.
The table below summarizes the common causes of high and low cell counts:
Images in this table are from Servier Medical Art. License: https://creativecommons.org/licenses/by/3.0/legalcode