Whether you have a cold or some other illness, your doctor will often ask you to do a blood test, right? We usually do a complete blood count (FBC). This gives a good idea of the number of cells in your blood. But sometimes, your doctor may want to look at your blood cells a little more closely, like a detective under a microscope, to see exactly what the shape, size, and color of those cells are like. That's why we call the special test for that a Peripheral Blood Smear (PBS) or "blood film test."
Simply put, what is this blood film test (PBS)?
A Peripheral Blood Smear (PBS) is a test that involves taking a drop of your blood, spreading it as a thin film on a glass slide, staining it using special dyes, and looking at it under a microscope.
The special thing about this is that instead of a machine giving a report like some blood tests, this one is checked by a trained Medical Laboratory Technologist (MLT) or Pathologist. This means that every little detail of your blood cells is examined with the human eye . Even small changes and unusual shapes of cells that a machine cannot pick up can be easily identified by a skilled eye.
Why would a doctor tell you to do this PBS test?
There may be several reasons why you might want to take this test.
Imagine that your complete blood count (FBC) report shows that your red blood cell, white blood cell, or platelet count is either significantly lower or significantly higher than normal. Your doctor will want to know, "Why is this happening?"
The FBC report is like the cover of a book. It gives you some basic information like the title of the book and the author. But to really know the story inside the book, you have to turn the pages and read, right? That's what PBS is like. PBS uses the clues provided by the FBC to see exactly what the 'story inside' of the blood cells is.
Also, you may be asked to do this test for several other reasons:
- Unexplained symptoms: If you have symptoms like constant fatigue, frequent fevers, and unexplained bruises, this test can help find the cause.
- Check the success of treatment: If you are undergoing treatment for a blood-related disease, a PBS test will be done to see if the treatment is successful and if your blood cells are returning to normal.
- Before a bone marrow transplant: This is also used to learn more about the condition of your blood cells and bone marrow before something like a stem cell transplant.
What can this test find out about our blood?
To understand what the PBS test looks for, let's first simply remind ourselves of the three main characters in our blood.
| Blood cell type | What you do is simple. |
|---|---|
| Red Blood Cells | These are the 'delivery service' that carries oxygen throughout our bodies. They take oxygen from the lungs and deliver it to every cell. |
| White Blood Cells | This is the 'army' in our body. It protects us by fighting germs (bacteria, viruses) that cause disease. There are 5 types of these people. |
| Platelets | Just like a 'plaster'. When we get injured, these are the ones who stop the bleeding and help the blood clot. |
In a PBS test, the microscope examines all three types of cells in detail. They focus primarily on:
- Changes in the size and shape of cells: For example, the shape of red blood cells can be changed, such as whether they are sickle-shaped or target-shaped. These changes can provide clues about various blood diseases.
- Changes in cell count: As with the FBC, this also looks at the number of cells. At the same time, it looks at whether the cells look "healthy" or "abnormal".
- Differences in white blood cell types: There are 5 types of white blood cells. The size of each type is specifically checked, whether there are any abnormalities in their appearance, and whether there are any immature cells (blasts).
- Parasites in the blood: Sometimes, parasites that cause diseases like malaria can be seen inside red blood cells. The PBS test is a very important test to diagnose malaria.
What diseases can the PBS test help identify?
This test is a very powerful tool used to diagnose many blood-related diseases.
Leukemia - Blood cancer
Our bone marrow is our 'blood-making factory'. When a large number of abnormal white blood cells start to form inside this factory, they crowd out healthy cells. These abnormal, immature cancer cells (blasts) can be clearly seen in a PBS test.
Anemia
Anemia is when the body does not have enough healthy red blood cells. This can happen for many reasons. In conditions like iron deficiency, vitamin B12 deficiency, or thalassemia, the shape and size of red blood cells change. These changes can be easily identified with a PBS and can provide guidance on finding the cause of the anemia.
Myelodysplastic Syndrome
This is also a cancer of the bone marrow. In this case, the bone marrow is unable to produce healthy, mature blood cells (red, white, or platelets). These abnormally shaped, misshapen cells are seen in the PBS.
Lymphoma - cancer of the lymph nodes
This is a cancer that develops in our lymphatic system. Sometimes these cancer cells can also enter the blood. If that happens, those abnormal lymphoma cells can be identified with the PBS test.
Infections and Autoimmune Diseases
When there is something in the body like a bacterial infection, a type of white blood cell (neutrophils) that fights it increases, and you can see changes in their appearance (toxic changes). Similarly, in viral infections like dengue, you can see changes in some types of white blood cells (lymphocytes). In autoimmune diseases (diseases in which our body's defense system attacks our own body), you can also see a decrease in the number of white blood cells or other changes.
Malaria
Malaria is caused by a parasite that enters our blood from a mosquito. This parasite lives inside our red blood cells. When viewed under a microscope in a PBS test, these parasites can be clearly seen inside the red blood cells. Therefore, this is an essential test in diagnosing malaria.
How is this test done? Does it hurt?
There's nothing to be afraid of about this. It's very simple.
1. Just like a normal blood test, a small blood sample is taken from a vein in your arm.
2. Then, a drop of blood is placed on a glass slide, and another slide is used to spread it as a thin film.
3. After it dries, it is stained with special pigments and examined under a microscope.
You will only feel a slight sting from the needle. Other than that, there is no other discomfort or pain associated with this test.
What should we understand from the information in the report?
This is the most important thing. When you receive your PBS report, don't be alarmed by the words on it. A Peripheral Blood Smear report is not a final diagnosis.
This is like one piece of a puzzle. To see the whole picture, you need to put together the other pieces, such as what the doctor has found out about you, your symptoms, and your FBC report.
The PBS report helps the doctor think further, confirm his suspicions, or decide what tests to do next.
Therefore, never be afraid to Google the words in the report and see what comes up . The same word can have different meanings in many diseases. Only the doctor who treats you knows how it fits your condition. So take the report, meet your doctor and talk about it. He will explain everything to you clearly and simply.
Take-Home Message
- A Peripheral Blood Smear (PBS) is a detailed test that looks at the shape, size, and appearance of your blood cells (red, white, and platelets) under a microscope.
- This is often done to investigate the cause of an abnormality in an FBC report.
- This test is very important for diagnosing anemia, blood cancer, various infections (such as malaria), and many other diseases.
- A PBS report is not a final diagnosis. It is just another piece of evidence that helps the doctor make a diagnosis.
- The best and only way to understand the results of your report is to talk to your doctor about it. Don't jump to conclusions based on information on the internet.
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