What Is Fecal Occult Blood and How to Use the Fecal Occult Blood Test Kit (FOBT)?
Although it is often preventable and treatable upon early detection, colorectal cancer is among the most common cancers and a major cause of cancer-linked mortality in the world. Since major delays can occur between the development of colorectal cancers and the onset of symptoms, regular screening proves to be critical for preventing cancer development and facilitating prompt treatment. With its various forms, fecal occult blood testing (FOBT) is among the primary detection methods that assist in the diagnosis of colorectal polyps, colorectal cancers, and other conditions that may cause gastrointestinal bleeding. Read along to learn more about fecal occult blood testing (FOBT) and how to use the Fecal Occult Blood Test Kit (FOBT).
What Is Fecal Occult Blood (FOB)?
Unlike other forms of blood in the stool, such as melena or hematochezia, fecal occult blood (FOB) refers to blood in stool that is not visibly apparent. Accordingly, fecal occult blood testing (FOBT) is a diagnostic method intended for the detection of subtle blood loss at any point across the gastrointestinal tract. The test results may inform on different forms of upper or lower gastrointestinal bleeding and call for further testing for various conditions such as peptic ulcers, polyps, sickle cell anemia, or cancer activity. While fecal occult blood testing (FOBT) does not directly detect malignancy in the gastrointestinal tract, it is a common and established method used for the clinical screening of colorectal cancers. Around 1-5% of the tested populations are estimated to receive a positive fecal occult blood test. Overall, it is a convenient and efficient method for the early detection and regular screening of both precancerous developments and cancer activity.
How Is Fecal Occult Blood (FOB) Detected?
Various testing options are available to screen fecal occult blood (FOB) in the stool. The method most suitable for a specific case may be decided based on the condition, medical history, family history, possible genetic syndromes, and preferences of the patient, together with the availability of resources necessary for testing and follow-up. Guaiac-based fecal occult blood test (gFOBT), fecal immunochemical test (FIT), and the FIT-DNA test are currently the primary methods for the detection of fecal occult blood (FOB) in the stool. Among these, the guaiac-based fecal occult blood tests (gFOBT) utilize chemical guaiac to check for heme in stool samples. On the other hand, fecal immunochemical tests (FIT) detect heme through antibodies. Although both the guaiac-based fecal occult blood test (gFOBT) and the fecal immunochemical test (FIT) can be performed at home or in other point-of-care settings with a simple stool sample obtained with a stick or brush, the collected samples are often required to be sent into a laboratory for the detection of occult blood. Combining the fecal immunochemical test (FIT) with the detection of altered DNA, the FIT-DNA test requires the collection of an entire bowel movement to be sent into a laboratory. Finally, some rapid chromatographic immunoassays, such as our FOB Rapid Test Kit, enable the qualitative detection of occult blood in stool in minutes. These tests are suitable for point-of-care screening as they do not require the collected samples to be sent to a laboratory for procession or interpretation.
What Can a Positive Fecal Occult Blood Test (FOBT) Mean?
A positive result with a fecal occult blood test (FOBT) may be caused by various medical conditions that present with upper gastrointestinal bleeding or lower gastrointestinal bleeding. Colorectal cancers or gastric cancers have been found to be the underlying condition in around 2-10% of the patients that test positive with a fecal occult blood test (FOBT). Colorectal cancer is a type of cancer that starts in the colon or rectum. It often emerges as polyps on the innermost lining of the colon or rectum, proceeds outwards into some or all layers of the wall, and develops into different tissues such as blood or lymph vessels. The stage of colorectal cancer is decided based on the depth of its growth into the wall and the state of its spread outside the colon or rectum. While adenomas or other types of polyps account for around 20-30% of the patients that test positive with a fecal occult blood test (FOBT), not all colorectal polyps indicate a pre-cancerous condition. Regular screening allows polyps to be effectively managed, and any malignancy can be promptly treated upon detection. In addition to colorectal cancers and polyps, other possible causes of a positive fecal occult blood test (FOBT) include diverticular disease, hemorrhoids, inflammatory bowel disease, and sickle cell anemia.
According to GLOBOCAN 2020, colorectal cancer was estimated to be responsible for approximately 10% of all new cases of cancer and 9.4% of all cancer-linked deaths. While colorectal polyps or cancer may not always cause symptoms if you experience blood in or on the stool, changes in bowel habits, diarrhea, constipation, persistent abdominal pain or cramps, unexplained weight loss, narrow ribbon-like stools, and the feeling that your bowels do not empty all the way, it is best to consult your healthcare provider and get tested. You are also strongly advised to get screened regularly if you are at higher risk for developing colorectal cancers due to your age, life history, or family history.
How to Use the Fecal Occult Blood Test Kit (FOBT)?
The exact procedure to be followed for detecting fecal occult blood (FOB) depends on the selected testing method. Guaiac-based fecal occult blood tests (gFOBTs) and fecal immunochemical tests (FITs) often require the collection of a stool sample with a stick or brush. Once the sample is collected, it is often smeared on one or multiple cards to be sent to a laboratory. On the other hand, the FIT-DNA test requires the collection of an entire bowel movement to be sent to a laboratory. Immunochromatographic assays, such as our FOB Rapid Test Kit, require the collection of liquid or solid stool specimens in a clean and dry container. Following its collection, the sample is transferred into the included tube containing the extraction buffer. Then, the cap of the tube is closed, the sample is thoroughly mixed with the extraction buffer, and the tube is left alone for a few minutes, as specified in the manual. Finally, the test cassette is removed from its pouch, and a few drops of the processed sample is added to the sample well (S) on the test cassette. The results can be read within the period specified in the manual, which is usually no more than 15 minutes.