Red alert

Posted on 6 March 2016

A full blood count test can alert your doctor to a number of issues. We find out what it entails.

Few bodily functions elicit as much emotion – or poetry – as blood. We love our family because blood is thicker than water; dealing with difficult people is like getting blood from a stone; not to mention your blood boiling, or running cold. Blood can also be fresh, young or even worth bottling. Blood is life – both figuratively and literally, as it transports oxygen around your body. It makes sense, then, that a full blood test could tell your doctor lots about your health.

What is blood?
Blood is your body’s courier system – it delivers oxygen and nutrients to cells and transports away waste products such as carbon dioxide. The blood cells are suspended in blood plasma, which is mostly water. Blood has three different types of cells: white blood cells, red blood cells and platelets. Dr Alicia Els, a haematology pathologist at Pathcare, explains: ‘White blood cells defend the body against infections and participate in the immune response. Red blood cells contain haemoglobin, a protein responsible for supplying oxygen to the different organs and tissues. Blood platelets are small fragments that form part of clots at sites of injury and bleeding.’

What is a full blood count?
A full blood count (also called a complete blood count) is a test requested by your doctor or another medical professional to evaluate the numbers of the three types of circulating blood cells, says Dr Els. It provides information about the cells, and can also show your doctor the concentration of minerals and proteins in your blood.

What can a full blood count detect?
‘The full blood count is a commonly requested test,’ Dr Els says. ‘It is requested to screen for a wide range of conditions and diseases, including different types of anaemia, infections, inflammatory conditions and blood cancers, for example leukemia.’
After your doctor gets the results from your full blood count, they may request further tests, for instance iron studies, to establish a diagnosis. The full blood count is also often used in monitoring medical conditions and treatments. ‘Various subtypes of white blood cells exist and a white blood cell differential count may be part of a full blood count,’ Dr Els adds. ‘Typically, the number of red blood cells will also be counted, as well as the total amount of haemoglobin.’

How is the test done?
Your doctor or a medical professional will draw a sample of blood by inserting a needle into a vein, typically in the crook of your arm. The sample is then sent to a lab for analysis, where a lab technician will most likely use an automated analyser to do the blood count. (In the past blood cells were counted manually by viewing a blood slide under a microscope).

0.2mg
This is roughly the amount of gold in your body – most of it in the blood.

Blood is red because of the protein haemoglobin in red blood cells. Haemoglobin contains iron, which binds with the oxygen in red blood cells, resulting in red blood. Some animals, such as octopuses and snails, have blue blood because their blood contains haemocyanin, which is copper-based.

DID YOU KNOW?
The ancient Greek philosopher and scientist Aristotle believed that the brain was used to cool blood, while intelligence was located in the heart.

1 minute
The average time it takes a red blood cell to make a complete circuit of the body. The time depends on your heart rate and the size of your heart.

120 days
The lifespan of a red blood cell, before being broken down and recycled by macrophages, a type of white blood cell. Platelets only survive for about 10 days.