Question and answers about clinical haematology.
What is clinical haematology?
Clinical haematology is the study of diseases of the blood and bone marrow, and how to treat them. Clinical haematologists diagnose and look after people with these diseases.
What is bone marrow
Bone marrow is the spongy inner part of bones. It acts as a “factory” to make blood cells. Many diseases of the blood are also diseases of the bone marrow. Often blood diseases can be diagnosed by taking a small sample of bone marrow and examining it under the microscope.
My doctor says I need a bone marrow test. What is this?
Haematology doctors often need to take small samples of bone marrow to help with diagnosis of certain blood disorders, and sometimes other disorders. This is a quick and simple procedure which can be carried out in the out patient clinic. Local anaesthetic is given to numb an area of skin usually over the pelvis (just above the buttock) and a needle is used to take a small sample of bone marrow. The procedure usually only takes about 15 minutes.
Sometimes people are given sedative drugs before the procedure and will need to stay an hour or two afterwards to allow these drugs to wear off. If you are given sedative medicines, you cannot drive for the rest of the day. If not, you can go back to work if you wish and have a normal day after the bone marrow test.
The samples taken are analysed by the haematology doctors. The results are usually available in about one week to ten days, sooner for some tests.
What does blood do and how does it work?
Blood is a transport system for the body, helping to move nutrients and energy to where they are needed and removing waste products from body tissues. Normal blood consists of blood cells, which float around in a watery mixture called plasma (19). The different types of blood cells and the plasma all have different functions.
What are Red Blood Cells
These are the most common blood cells. They give the blood its red colour. Red blood cells (RBC’s) are filled with a chemical called haemoglobin. The haemoglobin in the red blood cells transports oxygen (from the lungs, where it is breathed in from the air) around the body to all the other tissues like the heart, liver, kidneys and brain. Every tissue in the body (even fat and skin) needs oxygen to make energy so people who are short of haemoglobin feel tired and lacking in energy, because they cannot move the oxygen to where it is needed.
Red blood cells live for about 3 to 4 months, so every day your body produces millions of new red blood cells (from the bone marrow) to replace the ones that have died. This is normal and part of a natural “recycling” process.
Red blood cells make up about 40 - 50% of the volume of blood in your body; most of the rest is the watery plasma. Red blood cells can be given in a transfusion to people who lack them when this is necessary. However, usually, a lack of red blood cells can be treated by other methods. Some people can react to blood transfusions and so they are only used when absolutely necessary.
What are White Blood Cells?
White blood cells (WBC’s) are less common than red blood cells but are equally important. White blood cells are part of your body’s immune system and their most important job is to fight infections. Different types of white blood cells fight different types of infections.
The most common white blood cells are called neutrophils, and they help to fight off bacterial infections. Lymphocytes are another type of white blood cell, and mostly help to fight viral infections. There are other rarer white blood cells including eosinophils and basophils.
If you have an infection, for example in your lung, white blood cells are attracted to it and start to attack the infection. When you have an infection, your body will normally produce extra white blood cells to help fight it.
Some white blood cells normally only live for a few hours so your body produces new WBC’s every day. In particular, neutrophils often only live for 3 or 4 hours.
Many blood diseases can cause a lack of white blood cells. People who have too few white blood cells tend to be more susceptible to infection than normal. This is particularly the case with low levels of neutrophils, a condition called neutropenia (16). Because they only live a short time, it is very difficult to give WBC’s in a transfusion and WBC transfusion is not currently available in New Zealand.
Fortunately, modern antibiotics are usually very effective in fighting infection in people who have low levels of neutrophils.
What are Platelets?
Platelets are technically not proper cells but little bits broken off big cells. Platelets are part of a system which allows the blood to clot. (Certain chemicals in the plasma, called clotting factors, are also needed for the blood to clot.) If you cut yourself, platelets are attracted to the cut and begin to stick together with the help of the clotting factors, and a blood clot is formed.
People who lack platelets are more likely to bleed and bruise than normal. When necessary, platelets can be given in a transfusion to some people who lack platelets.
What is Plasma?
Plasma is the name given to the liquid that the blood cells float in. Plasma is mostly water with chemicals like salt and sugar dissolved in it. It also contains various proteins and other chemicals that are necessary for your body to function properly. Levels of salt, sugar and other chemicals can be abnormal for many reasons, including diseases of the liver or kidneys or other problems like diabetes.
One group of chemicals found in plasma are called the clotting or coagulation factors. These work with platelets (10) to allow the blood to clot when necessary. Some people can have abnormal amounts of these clotting factors. In some cases this can lead to a tendency for blood to clot when it should not (see blood clots (6)).
For other people, lack of certain clotting factors can lead to an increased risk of bleeding, for example in haemophilia (21).
Some people with low levels of clotting factors need plasma transfusions. These are given like a blood transfusion (22), and have similar possible side effects.
What do I need to know about blood transfusion?
Red blood cells, platelets and plasma are called blood components. They can all be given as transfusions if necessary. The blood components come from blood donations from members of the public. After blood is donated, it is tested to check the blood group and screened for infections such as hepatitis and HIV. Blood is then processed into separate parts; red blood cells, platelets and plasma.
If you need a “blood” transfusion, what you actually get is red blood cells. Platelets and plasma can also be given as transfusions. Occasionally people can have reactions to blood, usually causing shivers and a temperature. We can use various medicines to help ease these symptoms if they occur.