Having blood in your stool can be a bit scary for anyone. But did you know that sometimes blood can be present in your stool, even in amounts so small that it's hard to see? Today, we're going to talk about a very simple, yet very important test that checks for "hidden" blood that's not visible to the naked eye.
Simply put, what is a fecal occult blood test (FOBT)?
While the name may sound a bit scientific, the process is actually quite simple. A Fecal Occult Blood Test (FOBT) is a test that uses chemicals to look for tiny amounts of blood in your stool that are too small to be seen with the naked eye. The word "Occult" here means "hidden." This means it looks for blood that we can't see with the naked eye.
This test can only tell if there is blood in your stool. But it cannot tell exactly where the blood is coming from. Imagine that the test result is "Positive". This means that there is blood in your stool. This could be due to small growths (polyps) in your colon or rectum. Sometimes it can also be an early sign of colon cancer. But don't worry! This doesn't always have to be something serious. It can also be caused by some minor health conditions.
What are the causes of blood in the stool?
There can be several reasons for blood in the stool, both visible and invisible. Let's take a look at what they are.
| Possible reason | A simple explanation |
|---|---|
| Polyps in the colon | These can be benign or malignant. They can cause bleeding. |
| Hemorrhoids | Swelling of the blood vessels around the anus. These can become injured and bleed during bowel movements. |
| Anal fissures | Small cracks in the skin around the anus. These often occur in conditions such as constipation. |
| Intestinal infections and ulcers | Bleeding can occur due to infections or ulcers in the digestive system. |
| Inflammatory Bowel Disease | For example, conditions like ulcerative colitis and Crohn's disease can cause the lining of the intestine to become damaged and bleed. |
| Diverticular disease | Small pouches in the wall of the colon. These can bleed if they become infected. |
Sometimes the blood in the stool can be bright red. Other times it can be pitch black. This is called melena. However, the FOBT test is important for detecting blood that is not visible to the naked eye.
What are the methods for conducting this test?
There are several main ways to perform an FOBT test. All of them involve collecting and testing a sample of your stool.
1. Guaiac Card System (Guaiac FOBT - gFOBT)
In this, your doctor will give you a special card. All you have to do is, after you have had separate bowel movements for a few days, take a small sample of your stool with a small device and place it in the designated spot on the card. Usually, you are asked to take a three-day sample. Then, you need to take the card to the lab or to your doctor.
2. Immunochemical FOBT (FIT)
This is a new and more sensitive method. It involves collecting a stool sample in a special tube that you usually get. This is easier than the previous method. It also requires less restriction of food and drink before the test.
3. Flushable Reagent Pad Method
This is a kit that you can buy at a pharmacy without a prescription. In this, after you defecate, you need to put a special pad or tissue that has been coated with a chemical substance into the toilet bowl. If there is blood in the stool, the pad will change color. You can do this for about three days and report the results to your doctor.
How should you prepare before the test?
Your preparation greatly affects the accuracy of the results of this test. Therefore, it is extremely important to follow the doctor's instructions exactly. Especially if you are doing the gFOBT method, you need to take care of these things two to three days before the test.
The most important thing is to talk to your doctor before doing anything and follow his or her instructions exactly.
- Foods to avoid:
- Some raw fruits and vegetables (e.g. radishes, broccoli)
- Red meat (like beef and goat meat. It's okay to eat chicken and pork)
- Things to limit:
- Foods, drinks, and pills high in vitamin C (do not take more than 250 milligrams per day)
- Medications you are taking:
- Some pain medications (e.g., aspirin, ibuprofen) and iron supplements can cause false results. Therefore, tell your doctor about all medications you are taking. He or she will tell you whether you should stop taking them a few days before the test. Never stop taking any medications without first asking your doctor.
It is generally recommended to have this test at least once a year after the age of 45. This is especially important if you have not had a colonoscopy, which is a test for colon cancer.
What do the results say?
This is the biggest question everyone has. Let's see how to interpret the results.
If the result is positive
"Positive" means that there was blood in your stool sample. Don't be alarmed when you hear this. This does not mean that you have cancer. It just means that more tests are needed to find out what is causing the blood. Next, your doctor will probably recommend a test like a colonoscopy. This can look inside your entire colon to find out exactly where the blood is coming from and what is causing it.
If the result is negative
"Negative" means that there was no blood in the stool sample tested. This is good news. However, some cancers or tumors do not always bleed. Therefore, it is not a good idea to wait until the result is negative and not get tested again. It is important to get tested again at the scheduled time, as your doctor recommends.
Are there any false positives/negatives?
Yes, sometimes that can happen.
- False Positive (showing no blood): This can happen if you test during your period, if you have blood in your urine, if you have hemorrhoids that have ruptured and are bleeding. It can also be caused by certain foods and medications.
- False Negative (showing that blood was not present): Some tumors or cancers do not always bleed, so this can happen if you did not bleed on the days you took the sample.
That is why it is important to follow the doctor's instructions exactly and to repeat the tests at the scheduled time.
Take-Home Message
- A Fecal Occult Blood Test (FOBT) is a simple test that checks for hidden blood in the stool that is not visible to the eye.
- This is only a screening test for the early detection of diseases such as colon cancer.
- Don't worry if the result is "Positive." It doesn't mean a diagnosis, but that more tests are needed to find the cause.
- To obtain accurate results, follow the doctor's instructions regarding diet, drink, and medication carefully before the test.
- If you have any questions or concerns about this, discuss them openly with your doctor.
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