Blood test information
The following pages provide some information as to the meaning of the readings of your blood test results. Please note that normal values for any given blood parameter are given in the brackets next to your blood test result.
Please be aware that normal values may vary depending on age, gender and may be different between different laboratories.
FULL BLOOD COUNT (FBC)
Broadly speaking, the full blood count provides information about the 3 main cell types in our blood: red blood cells, white blood cells and platelets. This allows us to exclude conditions such as anaemia, infection and blood clotting disorders. The 3 blood cell types are suspended in liquid serum (plasma).
Please see below for more detailed information:
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Red Blood Cells (Erythrocytes)
These cells transport oxygen from the lungs to other organs of the body. The red blood cells then remove carbon dioxide from all areas of the body travelling back to the lungs where we breath out carbon dioxide, removing this substance from our body. There are specific features of red blood cells which can change in response to normal and pathological (potentially harmful) conditions in our body, for example the size, shape or concentration of the red blood cells. Red blood cells are produced in the bone marrow and have a life span of approximately 3 months. Detailed elements of the FBC relating to red blood cells include:*
Haemoglobin (Hb) is the protein found within red blood cells which carries out the oxygen: carbon dioxide gas exchange; the amount of haemoglobin within our red blood cells is possibly the most important internal factor in determining how well our body is supplied with oxygen. Iron is required to manufacture haemoglobin within the body. Therefore, if iron availability in the body is low, haemoglobin and so red blood cells cannot be produced, leading to the condition known as anaemia.
Mean cell volume (MCV) is a measure of the average volume of red blood cells. A low MVC is normally associated with a low iron count. Red blood cells with a smaller volume cannot carry such large quantities of oxygen, producing symptoms such as tiredness or shortness of breath. High MCV indicates larger than normal red blood cells and is usually caused by low levels of cobalamin (vitamin B12) and/ or folate (vitamin B9). During production in the bone marrow, red blood cells stay for longer before being released into the circulation, because of the missing vitamins in the blood cell formation process. The larger red blood cells are less efficient at carrying oxygen, having a lower haemoglobin concentration and usually are produced in smaller numbers. Both low MCV (microcytosis) and high MCV (macrocytosis) can result in anaemia. Deficiency of iron, vitamin B12 and folic acid can therefore result in different forms of the condition anaemia – defined as reduction in the number of red blood cells, or in the haemoglobin concentration within them. Macrocytosis can also be caused by excess alcohol consumption, liver
disease, thyroid disorder, side effect of medications and some other underlying rarer conditions.
Mean corpuscular haemoglobin (MCH) describes the average quantity of haemoglobin in an average red blood
cell. In conjunction with mean corpuscular haemoglobin concentration (MCHC), these values reflect the overall health of the haemoglobin in the blood. Low and high levels of MCH tend to correlate with microcytosis and macrocytosis respectively, being another parameter, which changes in accordance with different types of anaemia.
Haematocrit is reported as the number of blood cells as a total percentage of your blood. This is again part of the
assessment of the red blood cell function of your blood. Haematocrit may be low or high in conditions where there is a change in red blood cell production, where red blood cells have been lost (bleeding) or destroyed (sickle cell
disease), and in a number of chronic conditions, as well as from physiological conditions in the body such as being dehydrated.
White Blood Cells
Neutrophils are the first to respond to a bacteria or virus. They also send out messages alerting other cells of the immune system to mobilise and attack the foreign invader.
Lymphocytes come in 2 forms: B and T lymphocytes. B lymphocytes produce antibodies that “remember” an infection and target the “invader” directly. T lymphocytes eliminate body cells that have become infected by an “invader”.
Monocytes clean up dead cells.
Eosinophils fight off bacteria as well as being important in fighting parasitic infections. Eosinophils also play an
important role in allergic responses. When eosinophils mistake a substance such as pollen for a foreign invader, problematic allergic conditions such as hay fever can result.
Basophils also protect the body from infective intruders and cancer cells. Basophils also drive your body’s reaction to allergic triggers. Basophils cause cells to release histamine which causes narrowing of the airways of the lung and more generalised inflammation in the body.
Platelets
These are small colourless cell fragments that form to produce blood clots, and stop or prevent. When a blood vessel is
damaged, such as when we cut ourselves, a cascade of signals is sent out through the body, resulting in platelets travelling to the area of injury where a clot is formed and the vessel is repaired. Platelets also have a role in fighting infection by binding to invading infective cells and destroying them, such that platelet levels may fall during a serious infection.
ESR (Erythrocyte Sedimentation Rate)
This is a measure of how quickly red blood cells settle in the bottom of a test tube. Inflammation or infection in the body can increase the proteins in the blood; this will make red blood cells settle more quickly. Hence a high ESR is an indication of infection or inflammation in the body. This test is non-specific; this means the ESR could be elevated in the case of inflammation or infection anywhere in the body.
BIOCHEMISTRY
The biochemistry readings are measurements of chemical substances carried in the blood.
Urea – metabolism of amino acids, which are the building blocks of protein, leads to the formation of urea. It is excreted via the kidney. Levels can be raised with impaired kidney function or in people taking a very high protein diet.
Creatinine – this is also a breakdown product of protein. It is not affected by diet. It is a more specific indicator of kidney function.
Uric Acid – a waste product of protein digestion. Raised levels can suggest an increased risk for the development of gout.
Calcium – required in many metabolic processes including the normal action of muscle and heart. Most of the body calcium is in the skeleton. Raised levels may suggest a bone problem and reduced levels could reflect poor dietary intake, low level of Vitamin D or a bowel disorder. Corrected Calcium reflects the amount bound to protein and this is the most useful reading.
Phosphate – a mineral found in bone.
Total Protein, Albumin and Globulin – proteins that are made in the liver.
Alanine Transaminase (ALT) – an enzyme primarily made by the liver. Any inflammatory disorder of the liver can cause this enzyme level to rise.
Aspartate Transaminase (AST) – another enzyme made in the liver and also the heart.
y -Glutamyl Transferase (GGT) – an enzyme mainly found in the liver though also the kidneys and pancreas. It is a highly sensitive indicator of liver inflammation.
Alkaline Phosphatase (ALP) – an enzyme primarily found in the liver and bones. Ranges vary greatly during childhood and periods of bone growth. Very high levels can result from disease of either bone or liver.
Cholesterol – this is a substance produced naturally in the body. It is used by every cell in our body to maintain our health. About 20% of the cholesterol in our body comes from the food we eat. Cholesterol production, movement, and breakdown in our body is regulated by over 100 different genes, which is why up to 65% of the cholesterol levels for different individuals may be affected by their genetic predisposition.
Non-HDL cholesterol – Previously, the focus was on the LDL (‘bad’) cholesterol and HDL (‘good’) cholesterol levels, as well as the total cholesterol level. Research now tells us we also need to consider other parts of ‘bad’ cholesterol, known as IDL, VLDL and lipoprotein(a). These parts of ‘bad’ cholesterol are collectively known as ‘non-HDL’ cholesterol. This measurement has been shown to help calculate your risk of developing cardiovascular disease (such as heart attack or stroke) more effectively than before. As a guide, your non-HDL cholesterol should be lower than 4mmol/L and your total cholesterol should be 5mmol/L or less.
HDL Cholesterol (High Density Lipoprotein) ‘The Good Cholesterol’ – this takes cholesterol away from the body’s cells to the liver where it is either broken down or excreted.
LDL Cholesterol (Low Density Lipoprotein) ‘The Bad Cholesterol’ – it takes cholesterol from the liver to the body cells and when supply exceeds requirements it can lead to harmful build-up of cholesterol (atheroma).
HDL/LDL Ratio – the ratio of good to bad. Ideally this should be over 0.3.
Triglycerides – the chemical form in which most fat exists in food as well as in the body. Calories eaten and not used immediately by tissues are converted to Triglycerides and taken to fat cells to be stored. High levels are an independent risk for coronary artery disease. The level in blood tests is only useful if the blood test is taken whilst fasting.
Glucose – the energy source of the body. High levels suggest the presence of diabetes.
Ferritin – the protein which stores iron within the body. Most stored iron in the body is stored attached to Ferritin, which is present mainly in the liver but also in the bone marrow, spleen and muscles. A lower level of Ferritin suggests that taking a course of iron tablets
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