A 50-year-old man, Ah-Hung, recently took a fecal occult blood test subsidized by the Ministry of Health and Welfare, and the test came out positive, making him nervous about whether he had colorectal cancer. But then it occurred to him that he had eaten a bowl of duck's blood the night before the test, so he assumed that it should be caused by the blood of duck's blood and that he was fine, and so he didn't bother to follow up with a colonoscopy.

Positive fecal occult blood.

If there is blood in the feces that is visible to the naked eye, most people would be nervous and go to the doctor directly. However, when there is bright red blood in the feces that is visible to the naked eye, it means that the blood is stained after the feces are formed and there is no chance of oxidation with the mixing of the intestinal bacteria, so it's most likely a hemorrhoid or anal fissure, which would be less of a cause for concern.

But blood that has turned dark or black in the stool, which is less visible, less abundant, and less likely to change color, can indicate more dangerous diseases, such as diverticulitis, gastrointestinal ulcers, colorectal polyps, or colorectal cancer.

Although colorectal cancer tumors are supposed to have bright red blood because the stool rubs against the tumor, it is difficult to detect with the naked eye because the blood is usually not very large; and fecal occult blood testing is a way of checking for abnormal blood levels in the stool, which is a way of initially identifying colorectal disease.

Could fecal occult blood be due to "eating blood"?

In the past, the chemical method of fecal occult blood test (guaiac-based fecal oult blood test, g-FOBT) was used, which utilizes the peroxidase contained in red blood cells *** to produce a redox reaction and change the color of the reagent to identify the blood, and more than 6-20 grams of blood in the feces per day is considered positive. However, this practice is highly influenced by food and can easily lead to "false positives" or "false negatives.

Foods and medications that contain blood or iron, such as raw meat, offal, pig blood, duck blood, or fruits and vegetables high in vitamin C, such as spinach and grapes, or iron supplements and anticoagulants such as aspirin, can easily cause blood to be detected in the stool, resulting in a false positive.

However, most of the current tests are immunochemical fecal oult blood tests (i-FOBT), which use antibodies against antigens to detect the presence of human red blood cells, so that even if there is duck's blood in the feces, it is not interpreted as human blood, and iron is not used to detect the presence of human blood. Foods are even less likely to cause false positives, and are much more accurate than chemical methods.

Is fecal occult blood positive/negative for colorectal cancer?

A positive fecal occult blood test is not a 100% guarantee of colorectal cancer, but according to statistics from the medical team at National Taiwan University Hospital (NTUH), patients with colorectal cancer may have seven times more abnormalities on their i-FOBTs than the general population; and 40% of those with abnormalities on their i-FOBTs have been found to have intestinal ulcers, colitis, or polyps, colitis, or colorectal polyps. Or colorectal polyps, colorectal tumors, colorectal cancer.

But in fact, hemorrhoids, anal fissure bleeding, is the most common cause of bleeding, and then gastric ulcers, duodenal ulcers and other upper gastrointestinal ulcers, so many people will think that it is just "hemorrhoids", and are not willing to go to do time-consuming and laborious colonoscopy.

However, i-FOBT uses antigenic antibodies to read and red blood cells in the stomach and small intestine will break down blood proteins because of digestive juices, making the blood undetectable, so basically you can't tell if there is an upper gastrointestinal tract disease or not; hemorrhoids and anal fissures are bleeding, and in the big data, it was found that it doesn't affect the reading results of the i-FOBT,

So the i-FOBT can be used as a tool to help you find out if there are any problems with the blood cells in the stomach and small intestine. -FOBT positive, colonoscopy follow-up is recommended for all.

As for the negative i-FOBT, it's basically reassuring for the general public, but after all, i-FOBT can't detect colorectal cancer 100% of the time, so if you find that you've had very small stools for more than 7 days in a row or that you're experiencing diarrhea, constipation, weight loss, anemia, and other precursors to colorectal cancer, it's still recommended to have a colorectal exam. precursor symptoms such as anemia, it is still recommended to do colonoscopy to confirm , early detection, the cure rate of colorectal cancer can reach 90%.