The stool occult blood test, also known as occult blood test, is a test that assesses the presence of small amounts of blood in the stool that may not be visible to the naked eye and, therefore, serves to detect the existence of small bleeding in the digestive tract that may indicate ulcers, colitis or even colon cancer.
Generally, the collection of feces for this type of examination is requested by the doctor after the age of 40 or when there is a history of colon cancer in the family. In addition, the test can also be done to help diagnose inflammatory bowel problems, such as Crohn's disease or colitis, for example. Here's how to know if there's blood in your stool.
Main causes of occult blood in stool
If the test result is positive, there are several causes for the presence of blood in the stool, which include:
- Benign polyps in the intestine; Hemorrhoids; Ulcers in the stomach or duodenum; Ulcerative colitis; Crohn's disease; Diverticular disease; Colorectal cancer.
So, in order to identify the correct cause of the presence of blood in the stool, it is common that, after the occult blood test, the doctor orders a colonoscopy or an endoscopy, especially when the bleeding is not caused by hemorrhoids.
These two exams consist of the introduction of a thin tube with a small camera at the tip, which allows you to observe the inside of the intestine and stomach to identify possible injuries, facilitating the diagnosis. See even more about the main causes of blood in the stool.
How to prepare for the exam
The collection of feces for the occult blood test is usually done during 3 days, and during this period it is recommended to take some care with the diet, avoiding eating foods such as radish, cauliflower, broccoli, beets, beans, peas, lentils, chickpeas, corn, olives, peanuts, spinach or apples. It is important to consult the doctor and the laboratory regarding nutritional restrictions, as these may vary according to the technique used.
In addition, one should avoid taking drugs that irritate the stomach, such as anti-inflammatories or aspirin, for example, as they can cause bleeding and result in a false positive, in addition to supplements with vitamin C and iron. It is also recommended that the collection is not done less than 3 days after the menstrual period or when bleeding in the gums or nose has been verified, as the person may swallow the blood, for example. If the collection is made in any of these situations, it is important to inform the laboratory so that it does not interfere with the interpretation of the result.
The fecal occult blood test is considered a screening test, allowing evidence of the presence or absence of inflammatory bowel diseases to be identified without having to perform more expensive and invasive procedures. Despite this, the diagnosis of the disease should not be made based only on the result of the occult blood test, despite having high sensitivity, and a colonoscopy should be recommended, which is considered the "gold standard" test for the diagnosis of inflammatory diseases. intestinal infections, including colorectal cancer.
How to interpret the exam result
The possible results for the stool occult blood test are:
- Negative occult blood in stools: it is not possible to identify occult blood in stools, and the risk of having a gastrointestinal problem is low; Positive occult blood in the stools: indicates the presence of occult blood in the stools and, therefore, it is indicated to have a colonoscopy to identify the cause of the bleeding and to start the appropriate treatment.
In case of a positive or negative result with some changes, the doctor may request to repeat the test to confirm the result or perform a colonoscopy according to the person's clinical history.
False positive results are those in which the presence of blood is detected through the test, but which does not represent the patient's condition. This type of result can happen in people who do not prepare properly with regard to diet, have had gingival or nasal bleeding, have used drugs that cause irritation of the gastric mucosa, or have had the collection a few days after the menstrual period.
In some cases of negative results, the doctor may still request a colonoscopy if the patient is at high risk of developing colon cancer to ensure that there are no changes, as, although it is rare, there may be cancer without bleeding.
See other problems that can cause changes in stool in stool color.
