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Fecal occult blood test (FOBT)


Fecal occult blood refers to the blood that is hidden in the stool, which is invisible to naked eyes but can be detected under microscope.


Purpose of fecal occult blood test (FOBT)


Fecal occult blood occurs due to slow bleeding from the gastrointestinal tract. This blood is occult in nature and therefore does not change the colour of the stool. Your doctor shall advice fecal occult blood test under the following circumstances:


·         It’s a common screening test for colon cancer.


·         If you experience chronic abdominal pain then your doctor might recommend stool test


·         You might need to undergo fecal occult blood test if you have unexplained anemia as loss of blood from digestive tract could be a possible reason.


How to prepare for FOBT?


You need to prepare a week ahead before undergoing fecal occult blood test. Tell your doctor if you are taking blood thinners or NSAIDs. You doctor will ask you to stop taking these medicines a week before you undergo the test.


Make sure you tell your doctor if you are taking vitamin C supplements. The dose will either be reduced or you have to stop the supplements 3 days before the stool test.


Your diet will also be modified 3-4 days prior the test. You have to stop eating red meat like beef, pork, lamb, mutton and cut down on lean meat as well. Broccoli, turnips, horseradish, parsnip, cantaloupe, etc. should be avoided.


Apart from this, you need to tell your doctor if you have medical conditions like bleeding gums and rectal complications like haemorrhoids, fistula, diarrhoea, etc.


Women should not undergo fecal occult blood test during menstruation.


You doctor might also ask you to avoid using toilet paper, scented tissues, etc. as the chemical might interfere with test results.


How is FOBT performed?


The traditional approach is to collect the stool directly into containers which are readily available over the counter or any healthcare clinic. Different techniques for FOBT are:


Guaiac-based FOBT- This test entails use of a card coated with guaiac- a plant based matter that acts like an indicator for test results. The stool sample is collected on test card which is then analysed in lab for presence of occult blood. Change of colour in the test card means it’s positive.


Immunological FOBT kit- This is the latest technology and you can buy the kit from a pharmacy. Follow the instructions mentioned over the kit to undergo the test. The best part of IFOBT is- you do not require dietary modification or any other preparation. The test is based on an immunological assay.


OTC flushable reagent pad/tissue method- This is also a very simple technique that you can always opt for performing at home. The material is placed over the toilet bowl and you pass your bowel on it. The colour of the pad or tissue changes if blood is present in your stool.


What happens during FOBT?


Make sure your hands are clean or you wear disposable gloves while transferring the stool sample with the applicator onto the test kit.


You have to collect 3 stool samples every consecutive day and send it to the laboratory after labelling.


What happens after FOBT?


If your test is positive then you need to follow up medical check up like colonoscopy, gastrointestinal tests, etc. to rule out the underlying health condition.


Risk of FOBT


There are no risks involved in FOBT


Limitations of FOBT


Results might vary due to human errors like failing to perform the test as instruction or not following the diet. Chances of false negative test are also there.