What is ELISA in your blood report? (ELISA Test) Let's understand it simply

Have you ever been asked to bring a blood report when you went to a doctor for an illness? Have you ever been confused by the strange words on it? We often have experiences like this. Today, we are going to talk about a test method that we see in such reports, which may seem a little complicated, but is very important. That is the ELISA test.

What is ELISA simply?

Okay, let's first see what these four words ELISA mean. ELISA is an abbreviation for Enzyme- Linked I mmuno sorbent Assay . It sounds a little scary when you hear it, doesn't it? But don't be afraid of it. Simply put, ELISA is not a disease. It is a special testing method that is done in a laboratory. It's like a recipe for cooking.

This method can be used to detect very small things in our body fluids, such as blood, urine, and saliva. For example, this method is used to detect things like antibodies that our body makes against a particular germ (we call these antibodies), parts of the germ itself (we call these antigens), hormones, and proteins.

This method is so successful that doctors call it the "Gold Standard" of immunoassays. That means it is a very accurate and reliable method.

Think about the home pregnancy test that is used to check if you are pregnant. That also works on the principle of ELISA. It looks for the presence of the "pregnancy hormone" called HCG (Human Chorionic Gonadotropin) in the urine.

To understand this properly, let's first learn about 'Antigens' and 'Antibodies'.

To understand the ELISA method, we need to know about two very important characters in our body: Antigens and Antibodies.

What is an Antigen?

Think of a thief, an enemy, or a stranger entering our body. This stranger is what we simply call an antigen . These are usually things that are harmful to our body. These enemies called antigens can come in many forms.

• Viruses (e.g. dengue, HIV, coronavirus)
• Bacteria (e.g., bacteria that cause typhoid, tuberculosis)
• Parasites
• Things that cause allergies (e.g. dust, pollen, certain foods)
• Proteins on the surface of cancer cells

Each of these enemies has its own unique "identity card." That identity card is what we call an antigen.

What is an Antibody?

Now, when an antigen enters our body, our body doesn't just stand there. We have a very capable army inside our body. We call it the Immune System . We call the special soldiers in this army antibodies .

The specialty of these antibodies is that our body creates a special soldier (Antibody) to attack a specific type of thief (Antigen). Just like there is only one key that fits a single lock.

If the dengue virus enters the body, the body makes antibodies that only attack the dengue virus. If the HIV virus enters, it makes a different type of antibody that only attacks it. These antibodies go and attach to that enemy (antigen) and pass it on to other army cells to destroy it.

So what does the ELISA test look for?

ELISA can detect many things. It's like using the same device to do many different things. Your doctor will decide what to look for in an ELISA test based on your symptoms.

You can get a good idea about this from the table below.

How do you do the ELISA test in the lab?

The way this works is a bit technical. But I'll explain it to you with a very simple example. Imagine that your doctor suspects you have dengue and takes a blood sample from you to do an ELISA test. Here's what happens in the lab.

1. Preparing the enemy: First, the technician in the lab takes a special plastic plate and sticks the antigens of the dengue virus on it. Now our "enemy" is ready.

2. Collecting your blood: Next, your blood sample is added to this plate. If you have antibodies against dengue, they will stick to the dengue virus particles on the plate. Like a magnet. If there are no dengue antibodies, nothing will stick.

3. Washing: After that, this plate is washed thoroughly. What happens is that all the unnecessary things that are not attached to the virus are washed away. Only the attached antibodies remain.

4. Adding the "recognizer" antibody: Now comes the important part. Another type of antibody, specially made in the lab, is added to this. This antibody has an enzyme attached to it. This is the "Enzyme-Linked" part in the name. This second antibody will only stick to your antibodies that were previously attached to the plate.

5. Color reaction: Finally, a chemical substance is added to this that reacts with the enzyme and produces a color . Now, if you have dengue antibodies in your body and this whole process has happened, the color of that substance will change. If the color changes, the result is positive . If no color is produced, it means that you do not have dengue antibodies in your body. Then the result is negative .

Depending on the intensity of this color, you can roughly measure the amount of antibodies in the body.

How to interpret the results of the ELISA test?

Typically, an ELISA test can yield three types of results.

• Positive result: This means that what the test was looking for (e.g. an antibody or antigen) was present in your sample.
• Negative result: This means that what the test was looking for was not in your sample.
• Invalid result: This means that something went wrong during the test. It could be an error during sample collection or something that happened in the lab. If this happens, the test will need to be repeated.

Should I be worried if the result is abnormal?

Not at all. Just because your result is abnormal, meaning it's positive, doesn't mean you definitely have the disease. This is because ELISA tests have a small weakness. That's the possibility that sometimes false results can be obtained.

These are of two types:

• False-Positive Results: This is when the test reports that you have the disease, even though you don't actually have it. This false result can be caused by another medical condition or by another substance.
• False-Negative Results: This is when the test comes back "not sick" even though you actually have the disease. For example, this can happen if the test is done in the early days of an infection when the body has not yet produced enough antibodies.

For this reason, doctors often use ELISA as a screening test . That is, to separate people who may have the disease from those who do not. If the result is positive, the doctor will order another specific test (such as a Western Blot) to confirm it.

So, don't panic if you get an abnormal result. It's just one piece of a bigger puzzle. Your doctor will take your symptoms, medical history, and other tests into account before making a final decision. So, if you have any questions, don't hesitate to ask him.