What does fecal occult blood negative mean?

Basically everyone has bowel movements once a day, and the excrement is quite different. For example, if you eat something green today, the excrement you excrete is green. Sometimes we also excrete occult blood in the stool. You can't see blood in this kind of stool, but it has certain characteristics. So what does negative occult blood in the stool mean?

Fecal occult blood test is also called fecal occult blood test. It is a test used to check for hidden red blood cells or hemoglobin and transferrin in the stool. This is a very useful diagnostic indicator for checking gastrointestinal bleeding.

Occult blood in stool is an early warning of gastrointestinal abnormalities. When the amount of gastrointestinal bleeding is small, there may be no abnormal changes in the appearance of the stool and it cannot be identified by the naked eye. Therefore, patients suspected of having chronic gastrointestinal bleeding should undergo fecal occult blood examination, which is of great significance for the early screening of gastrointestinal malignancies (such as gastric cancer, colorectal cancer, polyps, and adenomas).

40% to 70% are intermittently positive, and in cases of gastrointestinal cancer (such as gastric cancer), the positivity rate can reach 95%, showing continuous positivity. Gastrointestinal bleeding caused by various other diseases may also show a positive reaction.

1. In the early stages of gastrointestinal malignancies, trace bleeding may be the only symptom; therefore, fecal occult blood testing is the only effective means of detecting gastrointestinal tumors in their early stages.

2. It is recommended that clinicians conduct three consecutive fecal occult blood tests on eligible patients to increase the positive detection rate.

3. It is recommended to choose products with appropriate sensitivity to minimize the false positive rate.

4. It is recommended to use different methods to jointly detect fecal occult blood to reduce the occurrence of false negatives.

Principle: The heme in hemoglobin has peroxidase activity, which can catalyze hydrogen peroxide, release new oxygen, oxidize the receptor reagent and develop color.

Advantages: Results are displayed quickly and clearly, and can be semi-quantitative.

Disadvantages: A. Poor specificity and greatly affected by diet. Foods and drugs containing ferrous ions can interfere with the results, with a false positive rate of 30%. Before the occult blood test, instruct patients to avoid taking iron supplements, animal blood, liver, lean meat and large amounts of green leafy vegetables for 3 days. If there is bleeding gums, do not swallow bloody saliva to prevent a false positive in the fecal occult blood test.

B. Low sensitivity, can only be detected when the bleeding volume is >90μg/ml.

C. There are many methodological restrictions: patients need a long time to prepare in advance. Due to different sampling sites, different reaction times and different judgments on color development, errors may also occur in experiments using the same method.