Elevated FOBT Results: Should You Worry About Colon Cancer?

Fecal occult blood test (FOBT) value greater than 30?

Hello, doctor.
Last month, during my company's health check-up, it coincided with the first day of my menstrual period.
I informed the nurse that I would submit my stool and urine samples later.
The nurse advised that it would be best to submit them as soon as possible, or it might delay the receipt of the health check report.
Therefore, I collected my stool sample on the last day of my menstrual period (which is not the two to three days after menstruation as per hospital guidelines, but the bleeding was nearly zero at that time) and submitted it to the hospital two days later.
I collected my urine sample on the same day I submitted it.
Recently, I received the report showing an FOBT value (chemical method) of 30.8 (the reference range on the report is 0-30), while the urine test results were normal.
Could this indicate a possibility of colorectal cancer? Last year's test result was less than 7, so I have become seriously anxious after seeing this report.
I tend to be constipated and have relatively hard stools, and occasionally I notice small streaks of blood due to anal fissures.
I remember that the stool sample collected that day was also quite hard, and I have a habit of straining during bowel movements.
Would you recommend doing another immunochemical fecal occult blood test? I can’t recall what I ate in the three days leading up to the sample collection, but I might have consumed red meat and dark green vegetables (I generally prefer vegetables and eat less meat).
However, I did consume imported cherry juice from Korea (which is said to be rich in iron), up to 70ml per day.
Could this have caused a positive test result? Over two years ago, I had a one-time incident of fresh blood after a bowel movement, but according to various doctors' responses, it was likely due to hemorrhoidal bleeding.
However, the current fecal occult blood value has made me very uneasy.
I have already scheduled an appointment with a gastroenterologist and am inclined to arrange for a colonoscopy, but I would still like to hear your advice first.
I am truly very anxious, and I thank you in advance!

YC, 30~39 year old female. Ask Date: 2022/11/24

Dr. Chen Shidian reply Gastroenterology and Hepatology

To address anxiety, a colonoscopy may be performed.
If the values are not high, there is no need to worry.

Reply Date: 2022/11/24

More Info

Elevated results from a Fecal Occult Blood Test (FOBT) can understandably cause anxiety, especially when there is a significant increase compared to previous tests. In your case, the FOBT value of 30.8, which exceeds the normal reference range of 0-30, raises concerns that warrant further investigation. However, it is essential to consider several factors before jumping to conclusions about the possibility of colon cancer.

Firstly, the FOBT is a screening tool designed to detect hidden blood in the stool, which can be a sign of various gastrointestinal issues, including polyps, hemorrhoids, or malignancies such as colorectal cancer. An elevated FOBT does not definitively indicate cancer; it merely suggests that further evaluation is necessary. The fact that your previous year's test result was less than 7 is a positive sign, but it does not eliminate the need for follow-up given the recent change.

Your menstrual cycle timing during the sample collection could potentially affect the results. While it is generally advised to avoid testing during menstruation due to the possibility of contamination, you mentioned that you collected the sample at the end of your period when the bleeding was minimal. However, it is still possible that residual blood could have influenced the FOBT result. Additionally, dietary factors can also impact the test outcome. Foods high in iron, such as red meat and certain fruits like cherries, can lead to false positives. Since you mentioned consuming cherry juice, this could be a contributing factor to the elevated result.

Regarding your symptoms, the occasional presence of blood due to anal fissures is not uncommon, especially if you experience constipation and have to strain during bowel movements. However, it is crucial to differentiate between benign causes of blood in the stool and more serious conditions. The fact that you have a history of anal fissures and have experienced minor bleeding could suggest that the FOBT result might not be related to a malignancy, but rather to these benign issues.

Given your elevated FOBT result and your symptoms, it is prudent to proceed with further testing. You have already scheduled an appointment with a gastroenterologist, which is an excellent step. A colonoscopy is the gold standard for evaluating the colon and can help identify any polyps, tumors, or other abnormalities directly. It is also a good opportunity to obtain biopsies if any suspicious lesions are found.

In terms of your anxiety, it is understandable to feel concerned about the possibility of colon cancer, especially with an elevated FOBT. However, it is essential to remember that many conditions can cause elevated results, and not all lead to cancer. The best course of action is to follow through with your scheduled appointments and tests.
In summary, while an elevated FOBT result can be concerning, it does not automatically indicate colon cancer. Factors such as menstrual contamination, dietary influences, and benign conditions like hemorrhoids or anal fissures could all play a role. Your proactive approach in seeking further evaluation through a gastroenterologist and potentially a colonoscopy is the right way to address your concerns. It is essential to stay informed and engaged in your health care, and I encourage you to discuss all your symptoms and concerns with your doctor during your upcoming visit.

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