The story your blood tells - Everything about the Complete Blood Count (CBC)!

Today we are going to talk about something very important to you and me. That is a test that is done on the blood in our body. Perhaps you have heard a doctor say, "Let's do a blood test" when you go to the doctor? One of the most common and important of these blood tests is the "Complete Blood Count (CBC)". This can tell us a lot about the little workers and guards inside our body. So, let's see what this `CBC` test is, why it is done, and what it tells us?

What is blood, and why is it so precious to us?

Imagine, our body is like a big city. There is a network of roads to transport goods, messages, and waste everywhere in this city, right? That's how the blood that runs through our veins is. There are so many amazing things inside this blood, it's like a small world! There are mainly three parts that we focus on in this `CBC` test.

Red Blood Cells - The lifeblood of our bodies

Do you know who carries the oxygen that comes into the lungs when we breathe to every tiny cell in the body, from the tip of our fingers to the brain cells? That great service is done by red blood cells, or `Red Blood Cells (RBCs). These are like small, round, indented discs. These are the ones that carry oxygen throughout the body, distribute it to every cell, and bring the waste product of those cells, `Carbon Dioxide`, back to the lungs. We get the energy to run, jump, work, and think because these red blood cells do their job properly. When these red blood cells are low, we say things like ``anemic'', ``pale'', ``a little tired'', ``feeling tired''. Doctors also call this condition `` anemia ''.

White Blood Cells - The Body's Defense Soldiers

Now look, when germs that cause diseases, such as bacteria, viruses, and fungi, try to enter our bodies, is there anyone to fight them? That's what white blood cells, or `White Blood Cells (WBCs), are for. These people are like the army and police in our country. These white blood cells are the most important part of our body's immune system .

There are several types of these white blood cells, and each type has a specific job assigned to it.

• Some white blood cells go straight to the germs and 'eat them up' (this is called `Phagocytosis`).
• Others make special proteins called `antibodies` against those germs. These antibodies attach to the germs and inactivate them.

So, when our body gets an infection, the number of these white blood cells increases to prepare for battle. Similarly, in some allergic conditions, some types of these white blood cells can also increase.

Platelets - the little heroes that stop bleeding

Do you remember when you fell while playing or cut your hand with a knife while cutting vegetables, and the bleeding stopped after a while? That's what platelets, or `Platelets` (another name is `Thrombocytes`), help with. These are not actually whole cells, but fragments that break off from larger cells in the bone marrow. But even though they are small, they do a big job. When a blood vessel is damaged somewhere and blood starts to leak out, these platelets are the ones that quickly come there and stick together, forming a mesh to close the wound. Just like when a hole forms in a culvert on a road, stones and sand are used to fill it. This is called blood clotting . If the number of these platelets decreases, it can be difficult to stop bleeding even from a small wound. Sometimes, the gums may bleed, and the body may simply turn blue in places (as if it was just hit).

So what is this Complete Blood Count (CBC) test?

Okay, now you have a little idea about the main soldiers and workers in your blood. So, this `Complete Blood Count (CBC)` is a test that counts how many of these red blood cells, white blood cells, and platelets are in a sample of your blood. Not only that, it can also measure other important information about these cells, for example, how big or small (that is, size) the red blood cells are, what their shape is, and how much hemoglobin `(Haemoglobin or Hb)`, the most important protein inside the red blood cells that carries oxygen, is. It also looks at how many of each type of white blood cells are there.

A doctor may order this ``CBC`` test for a variety of reasons.

• Find out if you have any illness: When you have symptoms such as fever, body aches, extreme fatigue, paleness, and frequent infections, this can help determine whether the cause is an infection, anemia, or some other problem.
• Check the status of an existing disease: In some diseases (e.g. leukemia, some autoimmune diseases), changes occur in the blood cells. So, the CBC also helps to see if the disease is under control and if the treatment is working.
• Check the effects of certain medications: Some medications (e.g., chemotherapy, antibiotics) can affect the bone marrow, which makes blood cells. So, when you are given those medications, this test is often done to see if they are causing any damage or reducing the number of blood cells.
• Before a major surgery: A CBC is important before an operation to check whether the blood count is adequate, whether the blood is able to clot properly, and whether there is an infection.
• As part of a routine health checkup: Even if there is no illness, sometimes a CBC can be done as part of an annual check-up to make sure everything is working properly in our body. There are times when it can help us identify early on a disease that may be starting inside us without us even realizing it.

What can we learn from a CBC test?

When you see a lot of numbers and letters in this `CBC` report, you may be thinking, "Oh, what is this?" Don't be afraid. Only your doctor can properly interpret this report and give you advice specific to your situation. But for general information, let's look at some of the main things it says.

Things to look at from the perspective of red blood cells (RBC):

• Red Blood Cell Count (RBC Count): This is the total number of red blood cells in the body. If this is lower than normal, it may indicate anemia.
• Haemoglobin (Hb): This is the protein inside red blood cells that carries oxygen. A decrease in this amount is also a major symptom of anemia. Normal values ​​vary for men, women, young children, and pregnant women.
• Hematocrit (Hct) / Packed Cell Volume (PCV): This tells you what percentage of your blood is made up of red blood cells. Simply put, it's like the 'thickness' of red blood cells in your blood. This also helps to determine if you have anemia. Doctors also pay attention to how this `PCV` value changes in diseases like dengue.
• MCV (Mean Corpuscular Volume), MCH (Mean Corpuscular Haemoglobin), MCHC (Mean Corpuscular Haemoglobin Concentration), RDW (Red Cell Distribution Width): These English letters tell you the average size of your red blood cells, the amount of haemoglobin (Hb) in a single red blood cell, how dense the haemoglobin is inside the red blood cells, and the size of the red blood cells (i.e. the variety of sizes). These are the things that your doctor can use to determine if you have anaemia, whether it is due to iron deficiency anaemia, vitamin B12 or folic acid deficiency (Megaloblastic Anaemia), a hereditary condition such as thalassaemia, or something else.

Things to look at in terms of white blood cells (WBC):

• White Blood Cell Count (WBC Count): This is the total number of white blood cells in the body. If this is higher than normal, it is often due to an infection or inflammation somewhere in the body. Sometimes, this number can be abnormally high in cancer conditions like leukemia. It is also a problem if this number is lower than normal. It can be due to some viral infections (e.g., early stages of dengue), bone marrow problems, or certain medications.
• Differential Count (DC): This indicates the percentage of five (mainly) different types of white blood cells.
• Neutrophils: These are the main soldiers that fight bacterial infections. Their percentage and absolute count increase during bacterial infections.
• Lymphocytes: These help fight viral infections and build immunity. In viral fevers like dengue, their percentage may increase, while the percentage of neutrophils may decrease (this is called `Relative Lymphocytosis`).
• Monocytes: These also work against infections, 'cleaning up' dead cells and germs.
• Eosinophils: These can be increased in allergic conditions (e.g. asthma, eczema, allergies to dust mites) and parasitic infections (e.g. pinworms).
• Basophils: These are also important in allergic reactions and some inflammatory conditions.

Things to consider from the platelets perspective:

• Platelet Count: This is the number of platelets that help the blood clot. If these are lower than normal (this is called `Thrombocytopenia`), there is a higher chance of bleeding. You may have heard about the decrease in these platelets during dengue fever. It can be dangerous. Also, if these are higher (`Thrombocytosis`), sometimes blood clots can form inside the blood vessels unnecessarily.

Very important: Each of these numbers has a "Normal Range." But you should know that those ranges can vary slightly from lab to lab, as well as depending on things like your age, gender, and altitude. So, to get the exact details of the numbers in your report, you should definitely talk to your doctor . Please don't assume that you have a disease just by looking at things on the internet or comparing them to a friend's report. That will only cause unnecessary fear.

How is the CBC test done? Is it something to be afraid of?

Now you may be wondering if this `CBC` test is something you have to do, or if it will hurt. There is nothing to be afraid of. It is very simple, and it takes just a few minutes.

It usually involves taking a small sample of blood from a vein in your arm (usually just below your elbow, where it's easily visible). This is done by a doctor, a trained nurse, or a medical laboratory technician in a lab.

1. First, the site where the blood will be drawn is thoroughly cleaned with a disinfectant such as alcohol.

2. Then, a small, thin needle (sterile needle) is carefully inserted into the vein, and the required amount of blood (about a few milliliters) is collected in a special tube. This tube contains a chemical substance (anticoagulant) that stops the blood from clotting.

3. After removing the needle, place a small piece of plaster or cotton wool on the area and hold it there for a while until the bleeding stops completely.

When the needle is inserted, it may feel like a small ant or mosquito stinging you . But it only lasts for a few seconds. After that, there is no pain. Some people are a little afraid of needles, which is normal. If you are like that, you can look away and take a deep breath while the blood is being drawn. This can help reduce the fear a little. Holding your hand for a while after the blood is drawn will also help reduce the chance of the area turning blue.

This blood sample is then sent to the lab, where the aforementioned cell types are counted and their details are examined. It can usually take a few hours, sometimes a day, for the report to arrive, depending on the workload of the lab.

So, what are the most important things we need to remember about this CBC? (Take-Home Message)

Okay, we've talked a lot about the `Complete Blood Count (CBC)` test. So, here are the main points you need to remember from all of this:

• A `CBC` is a very common and valuable test that measures the main types of cells in your blood, namely red blood cells, white blood cells, and platelets, as well as their other important characteristics (such as hemoglobin).
• This test helps you to diagnose certain diseases in your body (e.g. anemia, various infections, some cancers), see the current status of the disease, and monitor the effects of medications.
• Each type of cell in the blood has a specific job. Red cells carry oxygen, white cells protect against disease, and platelets stop bleeding. If any of these are lacking, our health can be affected.
• It is important to leave the interpretation of the numbers and letters in the `CBC` report to a doctor. The `Normal Range` may vary slightly from lab to lab. So, don't jump to conclusions and be unnecessarily scared or excited.
• Donating blood is a very simple thing that comes with a small, few-second pain. There's nothing to be afraid of.
• If you are sick or have any unexplained symptoms (e.g., persistent fatigue, frequent fevers, bleeding from various parts of the body), see a doctor immediately for advice. If necessary, he or she may order a ``CBC`` or other tests.

Finally, this `CBC` test is like a `mirror' that tells a lot about the little world inside our body, about our health. Therefore, it is a great help for us to have this test done at the right time, use the information obtained from it properly, and maintain our health. Wishing everyone good health!

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