Can Stool Tests Detect Polyps or Colon Cancer Risks?

Can fecal occult blood testing detect the presence of polyps?

Today, I followed your advice and took a fecal occult blood test.
When I asked the doctor some related questions, I was taken aback by his response.
He said that the fecal occult blood test cannot determine whether there are polyps in the intestines and mentioned that even if the test result is negative, there is still a possibility of having colorectal cancer.
He stated that the accuracy of the test is only about 30%! When I asked him why I felt like there was something pressing against my anus, he couldn't provide a clear answer.
Therefore, I would like to inquire whether the fecal occult blood test can detect any issues with polyps.
I hope the doctor I consulted was just someone who didn't understand much, and that I don't actually have to undergo a colonoscopy.
I really don't want to do that.
Thank you for your guidance.

ds2007wwe, 30~39 year old female. Ask Date: 2021/03/11

Dr. Chen Shidian reply Gastroenterology and Hepatology

The immunochemical fecal occult blood test has high accuracy and should be used for initial screening.
Domestic research reports indicate that 96.4% of patients with colorectal cancer tested positive using the immunochemical method.

Reply Date: 2021/03/11

More Info

Stool tests, particularly the fecal occult blood test (FOBT) and its more advanced version, the fecal immunochemical test (FIT), are commonly used screening tools for colorectal cancer. However, it's essential to understand their limitations and the context in which they are used.

Firstly, stool tests are designed to detect hidden blood in the stool, which can be an indicator of colorectal cancer or significant polyps. However, these tests do not directly detect polyps themselves. Polyps are abnormal growths in the colon that can potentially develop into cancer over time. While the presence of blood in the stool can suggest the presence of polyps or cancer, a negative stool test does not guarantee that polyps are absent. This is because not all polyps bleed, and some cancers may not present with blood in the stool initially.

Regarding the accuracy of stool tests, it is true that their sensitivity can vary. Studies suggest that the sensitivity of FOBT for detecting colorectal cancer can be around 70-80%, but this can drop significantly for detecting polyps, especially smaller ones. This means that while a positive result may warrant further investigation, a negative result does not rule out the possibility of colorectal cancer or polyps. Therefore, it is crucial to consider stool tests as part of a broader screening strategy rather than a standalone diagnostic tool.

In your case, if you are experiencing symptoms such as a sensation of something pressing against the rectum, it is essential to discuss these symptoms with your healthcare provider. While this sensation could be due to various benign conditions, such as hemorrhoids or anal fissures, it could also indicate more serious issues that warrant further investigation.

Given your family history of colorectal cancer, it is advisable to be proactive about screening. While stool tests are a good starting point, they should ideally be complemented by other screening methods, such as colonoscopy, especially if you have risk factors or concerning symptoms. Colonoscopy allows for direct visualization of the colon and the opportunity to remove polyps during the procedure, which is not possible with stool tests.

In summary, while stool tests are valuable for screening for colorectal cancer, they have limitations in detecting polyps directly. A negative stool test does not eliminate the risk of colorectal cancer, especially in individuals with a family history or symptoms. It is essential to maintain open communication with your healthcare provider about your concerns and consider a comprehensive approach to screening that may include colonoscopy, particularly if you have symptoms or risk factors. Regular screening is crucial for early detection and prevention of colorectal cancer.

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