Colorectal Cancer Screening: How to Properly Take a Stool Sample

Fact checked by Nick Blackmer

• More than 10% of fecal immunochemical tests (FIT) have unusable samples putting people at risk for missing early cancer markers.

• FIT looks for blood in the stool and is different from Cologuard, which checks for blood and DNA markers.

• The key to taking an adequate FIT stool sample includes following the instructions and submitting the sample no later than 48 hours after it’s taken.

Do you know how to correctly take a stool sample?

New research found that more than 10% of fecal immunochemical tests (FIT) used for routine colorectal cancer (CRC) screening had unusable samples that could not be tested.

The new study, published earlier this month in Cancer Epidemiology, Biomarkers and Prevention, found that as many as 51% of the samples that could not be tested were not collected properly. Other issues included incomplete labeling (27%), old samples (13%), or broken or leaking containers (8%).

FIT, which is used to check for blood in the stool, is often collected at home and is an accessible cancer screening option—especially for lower-income or uninsured people.

“These tests are relatively inexpensive, sensitive, easy to perform, and do not require any special preparation unlike a colonoscopy,” Subhankar Chakraborty, MD, PhD, a gastroenterologist with The Ohio State University Comprehensive Cancer Center—James Cancer Hospital and Solove Research Institute told Health.

“[They also] are non-invasive and can be done in the privacy of one’s home,” he said.

When the samples are not usable or are not completed at all, it could lead to undiagnosed colon cancer and pre-cancerous polyps.

“In turn, this puts [people] at risk of missing an early-stage cancer, which would be potentially curable,” Chakraborty said.

Here’s how to properly take a stool sample, as well as what can be done to improve this type of testing for colorectal cancer.

Related: Bristol Stool Chart for Healthy Poop

How to Take an Accurate Stool Sample

Since colorectal cancers are not always associated with obvious symptoms, accurate screening is crucial.

“The American Cancer Society recommends those at average risk get screened starting at age 45 since colorectal cancer is on the rise in younger people,” Paul Limburg, MD, chief medical officer for screening at Exact Sciences, the makers of Cologuard, told Health.

If your healthcare provider recommends FIT, they are likely to give you the Polymedco OC-Auto FIT, explained Rasmi Nair, MBBS, PhD, one of the study’s authors and an assistant professor at the Peter O’Donnell Jr. School of Public Health of UT Southwestern Medical Center.

“The FIT kit typically includes an outer envelope, a sampling bottle, collection paper, question and answer brochure, return mailer (envelope), a biohazard bag, and an absorbent pad,” she said.

Once you have read through the packet and instructions provided and are ready to take a stool sample, Nair recommends placing the collection paper on top of the water in the toilet and then depositing a stool sample on top of the collection paper.

Then, follow the instructions carefully. The process generally looks like this:

1. Use the tip of the wand (attached to the cap of the collection bottle) to scrape the surface of the stool before it touches the water.

2. Cover the grooved portion of the wand completely with stool.

3. Place the wand with the stool back in the sampling bag and close it.

4. Flush the remaining stool (and biodegradable collection paper) down the toilet.

After the sample has been collected and securely closed in the sampling bottle, Nair explained it’s important to wrap the sampling bottle in the small absorbent pad and place it in the biohazard bag.

Then, seal the biohazard bag and place it in the return mailer envelope. Make sure to include your name and date of birth as well as the date and time the sample was collected.

“Once collected, please return the completed kit by mail or in person to your clinic on the same day or at least within 48 hours of collecting your sample,” Nair said.

Keep in mind that too little stool, as well as too much stool, can make the sample unusable, Kyle S. Eldredge, DO, a board-certified and fellowship-trained colorectal surgeon with privileges at multiple Wellington and Royal Palm Beach, Florida hospitals told Health.

Are FIT and Cologuard the Same Thing?

Most people are familiar with Cologuard, but it is a different type of stool test than FIT. In addition to looking for blood in the stool like FIT, it also looks for DNA markers that could indicate cancer or pre-cancer.

Limburg explained that by adding this DNA component, the multi-target Cologuard test can detect more cancers or pre-cancers than single-target FIT tests. It can also be repeated every three years, while FIT testing needs to be repeated every year.

What Can Be Done to Improve Testing?

Of the nearly 57,000 patients in the new study, 5,819 had an unsatisfactory FIT. This means that those FIT tests couldn’t be processed by the laboratory.

What’s more, non-Hispanic Black patients were more likely to have an unsatisfactory FIT compared to non-Hispanic Whites, which is likely associated with multiple barriers to care, Nair explained.

To reduce the number of unusable samples, she suggests more robust patient education strategies and wordless, visual instructions to improve patient handling of stool samples.

“System solutions, such as affixing a patient name or unique test order bar code onto the FIT also can minimize the common ‘no patient name’ or ‘no date’ errors,” she said.

Other strategies may include automated test kit distribution for unsatisfactory stool tests, administrative registries that identify incomplete tests in addition to any abnormal results, and patient navigation to reduce gaps and disparities in CRC screening.

“The most important test is the test that gets done,” Eldredge said. “There needs to be a mechanism in place that if there is an unsatisfactory sample, that the patient will have adequate follow up to be provided a new sample kit, and improved guided steps to make the next sample satisfactory.”

Related: Study Identifies 4 'Red Flag' Symptoms of Colon Cancer in Younger People

Who Should Not Use FIT?

According to Chakraborty, the FIT test is for people who do not have colon cancer or signs or symptoms suspicious of possible colon cancer.

“If someone has symptoms like abdominal pain, weight loss, blood in stool, diarrhea they need a diagnostic colonoscopy,” he said.

Additionally, your healthcare provider may not want to use FIT if you have bleeding hemorrhoids, have known inflammatory bowel disease, or have a history of colon cancer in your family.

“These people are at a high risk for developing colon cancer and in them colonoscopy is the preferred test,” Chakraborty explained.

Related: How to Reduce Your Colon Cancer Risk

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