Blood Tests, Blood Testing and Blood
To find a specific blood test, simply click on the 'A-Z of Tests' to the right of this page.
What is a blood test?
A blood test can be very useful in helping to diagnose and detect medical conditions and illnesses such as diabetes, prostate cancer, heart disease, hormone imbalances, liver function, vitamin levels, ovarian cancer and various genetic conditions and disorders. At MediChecks we have over 1200 different types of blood tests, urine tests and many other types of tests.
Blood tests can also be used to monitor conditions such as thyroid disorders, diabetes and medical conditions relating to blood clotting irregularities. A useful type of monitoring blood test is a tumour marker test. Tumour marker blood tests are mostly used to monitor cancers and how they are responding to treatment.
How is a blood test carried out?
Blood samples can be taken either from a vein or from an artery. If only a few drops of blood are needed it is enough to make a small prick in the tip of the finger and then squeeze the blood out.
Most blood test samples are taken from a vein. The vein used for blood sampling is usually on the inside of your elbow or back of your wrist. A tourniquet (tight band) is usually placed around your upper arm. This makes the vein fill with blood and makes it easier for the blood sample to be taken.
The injection site is cleaned with swab usually containing spirit and then a needle is carefully inserted into the vein.
The needle will be attached either to a low pressure blood test tube (Vacutainer), or to a syringe where the plunger is pulled back to create low pressure.
When the required amount of blood has been extracted, the needle is carefully removed and a swab or piece of cotton wool is held over the wound. After one or two minutes the cotton wool or swab is removed and a sticking plaster is applied.
What are the main different types of blood samples?
Different blood tubes are used for different types of blood tests. For some blood tests the blood needs to clot and for other blood tests the blood is added to some chemicals to prevent the blood from clotting. If the blood glucose is being measured, then the blood is added to a special preservative, etc. Blood tubes come in different sizes and colours depending on the blood test that need to be performed on the blood.
The main types are:
- Serum
- Whole Blood
- EDTA ( Ethylenediaminetetraacetic acid)
- Sodium Citrate
- Heparin
- Fluoride
What is blood?
The average adult has about five litres of blood living inside of their body, coursing through their vessels, delivering essential elements, and removing harmful wastes. Without blood, the human body would stop working.
Blood is the fluid of life, transporting oxygen from the lungs to body tissue and carbon dioxide from body tissue to the lungs. Blood is the fluid of growth, transporting nourishment from digestion and hormones from glands throughout the body. Blood is the fluid of health, transporting disease fighting substances to the tissue and waste to the kidneys.
Because it contains living cells, blood is alive. Red blood cells and white blood cells are responsible for nourishing and cleansing the body. Since the cells are alive, they too need nourishment. Vitamins and Minerals keep the blood healthy. The blood cells have a definite life cycle, just as all living organisms do.
Approximately 55 percent of blood is plasma, a straw-coloured clear liquid. The liquid plasma carries the solid cells and the platelets which help blood clot. Without blood platelets, you would bleed to death.
When the human body loses a little bit of blood through a minor wound, the platelets cause the blood to clot so that the bleeding stops. Because new blood is always being made inside of your bones, the body can replace the lost blood. When the human body loses a lot of blood through a major wound, that blood has to be replaced through a blood transfusion from other people.
But everybody's blood is not the same. There are four different blood types or blood groups. Plus, your blood has Rh factors which make it even more unique. Blood received through a transfusion must match your own. Patients who are scheduled to have major surgery make autologous blood donations (donations of their own blood) so that they have a perfect match.
Red blood cells perform the most important blood duty. A single drop of blood contains millions of red blood cells which are constantly travelling through your body delivering oxygen and removing waste. If they weren't, your body would slowly die.
Red blood cells are red only because they contain a protein chemical called haemoglobin, which is bright red in colour. Haemoglobin contains the element Iron, making it an excellent vehicle for transporting oxygen and carbon dioxide. As blood passes through the lungs, oxygen molecules attach to the haemoglobin. As the blood passes through the body's tissue, the haemoglobin releases the oxygen to the cells. The empty haemoglobin molecules then bond with the tissue's carbon dioxide or other waste gases, transporting it away.
Over time, the red blood cells get worn out and eventually die. The average life cycle of a red blood cell is 120 days. Your bones are continually producing new blood cells, replenishing your supply. The blood itself, however, is re-circulated throughout your body, not being remade all of the time.
Since the human body is continually making more blood, it is safe for healthy adults to donate blood. The blood is then stored for use in emergency situations. Initially after giving blood, the donor may feel some momentary light-headedness due to the loss of oxygen-rich red blood cells and blood sugar. The body quickly stabilises itself.
Whenever a germ or infection enters the body, the white blood cells snap to attention and race toward the scene of the crime. The white blood cells are continually on the lookout for signs of disease. When a germ does appear, the white blood cells have a variety of ways by which they can attack. Some will produce protective antibodies that will overpower the germ. Others will surround and devour the bacteria.
The white blood cells have a rather short life cycle, living from a few days to a few weeks. A drop of blood can contain anywhere from 7,000 to 25,000 white blood cells at a time. If an invading infection fights back and persists, that number will significantly increase.
A consistently high number of white blood cells is a symptom of Leukaemia, a cancer of the blood. A Leukaemia patient may have as many as 50,000 white blood cells in a single drop of blood.
It's a straw-coloured, clear liquid that is 90 percent water, and it is an essential ingredient for human survival.
It might seem like plasma is less important than the blood cells it carries. But that would be like saying that the stream is less important than the fish that swims in it. You can't have one without the other.
Besides water, plasma also contains dissolved salts and minerals like calcium, sodium, magnesium, and potassium. Microbe-fighting antibodies travel to the battlefields of disease by hitching a ride in the plasma. Without plasma, the life-giving blood cells would be left floundering without transportation. Never underestimate the importance of plasma.
The human body does not handle excessive blood loss well. Therefore, the body has ways of protecting itself. If, for some unexpected reason, sudden blood loss occurs, the blood platelets kick into action.
Platelets are irregularly shaped, colourless bodies that are present in blood. Their sticky surface lets them, along with other substances, form clots to stop bleeding.
When bleeding from a wound suddenly occurs, the platelets gather at the wound and attempt to block the blood flow. The mineral calcium, vitamin K, and a protein called fibrinogen help the platelets form a clot.
A clot begins to form when the blood is exposed to air. The platelets sense the presence of air and begin to break apart. They react with the fibrinogen to begin forming fibrin, which resembles tiny threads. The fibrin threads then begin to form a web-like mesh that traps the blood cells within it. This mesh of blood cells hardens as it dries, forming a clot, or "scab."
Calcium and vitamin K must be present in blood to support the formation of clots. If your blood is lacking these nutrients, it will take longer than normal for your blood to clot. If these nutrients are missing, you could bleed to death. A healthy diet provides most people with enough vitamins and minerals, but vitamin supplements are sometimes needed. |
