Colorectal Cancer Screening: FIT Test & Stool Sample Guide
📊 Quick Facts About Colorectal Cancer Screening
💡 Key Takeaways About Colorectal Cancer Screening
- Early detection saves lives: Colorectal cancer is highly treatable when found early, with 5-year survival rates above 90% for localized disease
- Simple home test: The FIT test requires only a small stool sample collected at home - no bowel preparation or dietary restrictions needed
- Annual testing is crucial: Regular yearly screening provides the best protection as cancers may develop between tests
- Positive test requires follow-up: A positive FIT result needs colonoscopy - but most positive results are NOT cancer
- Start at age 45: Current guidelines recommend beginning screening at 45 for average-risk adults
- Family history matters: Those with close relatives who had colorectal cancer may need earlier or different screening
What Is the FIT Test for Colorectal Cancer?
The FIT test (Fecal Immunochemical Test) is a screening test that detects hidden blood in stool samples, which can be an early sign of colorectal cancer or precancerous polyps. It uses specific antibodies to identify human hemoglobin in stool, making it more accurate than older screening methods.
Colorectal cancer, which includes cancer of the colon and rectum (also called bowel cancer), is the third most common cancer worldwide and the second leading cause of cancer death. However, it is also one of the most preventable cancers when detected early through regular screening. The FIT test represents a major advancement in making screening accessible to everyone.
Unlike older guaiac-based fecal occult blood tests (gFOBT), the FIT test specifically detects human blood proteins, which means it is not affected by dietary factors like red meat or certain vegetables. This specificity makes it more convenient for patients and more accurate in detecting clinically significant bleeding from the lower gastrointestinal tract.
The test works by detecting hemoglobin, the oxygen-carrying protein in red blood cells. When polyps or cancers in the colon or rectum bleed, small amounts of hemoglobin may be present in the stool. The FIT test can identify even tiny amounts of blood that are invisible to the naked eye, which is why it is called an "occult" (hidden) blood test.
Understanding how colorectal cancer develops helps explain why screening is so effective. Most colorectal cancers begin as small, benign growths called polyps on the inner lining of the colon or rectum. Over time, typically 10-15 years, some of these polyps can undergo changes that transform them into cancer. By detecting and removing polyps before they become cancerous, or by finding cancers at an early stage, screening dramatically improves outcomes.
How Does the FIT Test Differ from Other Screening Methods?
Several screening options exist for colorectal cancer, each with different advantages. The FIT test is often recommended as the primary screening method because of its combination of effectiveness, convenience, and accessibility. Unlike colonoscopy, which requires bowel preparation, sedation, and a clinical visit, the FIT test can be completed at home in just a few minutes.
Colonoscopy remains the gold standard for detecting polyps and cancers, as it allows direct visualization of the entire colon and removal of precancerous growths during the same procedure. However, colonoscopy is more invasive, requires time off work, and has higher costs. The FIT test serves as an effective first-line screening that can identify those who need further investigation with colonoscopy.
The choice between screening methods should be made in consultation with a healthcare provider, taking into account individual risk factors, preferences, and access to healthcare services. What matters most is that screening is performed regularly according to recommended intervals.
| Screening Method | Frequency | Advantages | Considerations |
|---|---|---|---|
| FIT Test | Annual | Non-invasive, home collection, no prep needed | Positive results require colonoscopy follow-up |
| Colonoscopy | Every 10 years | Direct visualization, can remove polyps | Requires bowel prep, sedation, time off work |
| Flexible Sigmoidoscopy | Every 5 years | Less invasive than colonoscopy | Only examines lower third of colon |
| Stool DNA Test | Every 3 years | Detects DNA markers plus blood | Higher cost, more complex collection |
Who Should Get Screened for Colorectal Cancer?
Adults aged 45-75 at average risk should undergo regular colorectal cancer screening. Those with increased risk factors such as family history, inflammatory bowel disease, or genetic syndromes may need to start screening earlier and should discuss personalized screening plans with their healthcare provider.
Current guidelines from major medical organizations, including the US Preventive Services Task Force (USPSTF), American Cancer Society, and European Society of Gastrointestinal Endoscopy, recommend that colorectal cancer screening begin at age 45 for adults at average risk. This represents a change from previous recommendations that suggested starting at age 50, reflecting the concerning increase in colorectal cancer rates among younger adults.
Screening is recommended to continue through age 75 for most adults. For those aged 76-85, the decision to screen should be individualized based on overall health, life expectancy, previous screening history, and personal preferences. Adults over 85 are generally not recommended to undergo routine screening, as the potential harms may outweigh the benefits.
Understanding your personal risk level is essential for determining the most appropriate screening approach. Risk factors are typically categorized into average risk and increased risk, with different screening recommendations for each group.
Average Risk Individuals
Most people fall into the average risk category. You are considered average risk if you have no personal history of colorectal cancer or adenomatous polyps, no first-degree relatives (parents, siblings, or children) with colorectal cancer, no personal history of inflammatory bowel disease (ulcerative colitis or Crohn's disease), and no confirmed or suspected hereditary colorectal cancer syndromes.
For average-risk individuals, the FIT test performed annually is an excellent screening option. This approach has been shown in multiple studies to significantly reduce colorectal cancer mortality when performed consistently year after year. The key to effectiveness is adherence to the annual schedule.
Increased Risk Individuals
Certain factors place individuals at increased risk for colorectal cancer, requiring earlier or more intensive screening. These risk factors include having a first-degree relative diagnosed with colorectal cancer or advanced adenoma, especially if diagnosed before age 60. Personal history of adenomatous polyps, particularly large or multiple polyps, also increases risk.
Individuals with inflammatory bowel disease affecting the colon, such as ulcerative colitis or Crohn's colitis, have a significantly elevated risk that increases with the duration and extent of disease. Those with known hereditary syndromes such as Lynch syndrome (hereditary non-polyposis colorectal cancer) or familial adenomatous polyposis (FAP) require specialized surveillance programs typically involving colonoscopy at younger ages and more frequent intervals.
Contact your healthcare provider to discuss personalized screening recommendations if you have: a parent, sibling, or child diagnosed with colorectal cancer; a personal history of polyps or inflammatory bowel disease; a known genetic syndrome in your family; or unexplained symptoms such as blood in stool, persistent changes in bowel habits, or unexplained weight loss.
How Do You Collect a Stool Sample for the FIT Test?
Collecting a stool sample for the FIT test is simple and takes only a few minutes. You will use the provided kit to collect a small sample during a regular bowel movement, then seal it in the tube and mail it to the laboratory. No special diet or bowel preparation is required.
One of the major advantages of the FIT test is its simplicity. Unlike older stool tests that required dietary restrictions or colonoscopy that requires extensive bowel preparation, the FIT test has no special requirements. You can eat normally and take most medications before and during sample collection.
When you receive your FIT kit, it will contain all necessary materials including a collection tube with a sampling stick, collection paper or device to catch stool, a laboratory form, and a prepaid mailing envelope. The specific instructions may vary slightly between different kit manufacturers, but the general process is similar.
Step-by-Step Collection Instructions
- Prepare for collection: Before having a bowel movement, place the collection paper in the toilet bowl if provided. Alternatively, you may use a clean, dry container to catch the stool. Avoid contaminating the sample with urine or toilet water.
- Collect the sample: After your bowel movement, use the sampling stick attached to the tube cap to collect a small amount of stool. Most kits require you to scrape or poke the surface of the stool in several places to obtain an adequate sample.
- Seal the sample: Insert the sampling stick back into the collection tube and close it securely until you hear or feel it click. The tube contains a preservative solution that stabilizes the sample for transport.
- Complete the form: Fill out the laboratory form with your personal information and the date of sample collection. Accurate information ensures proper processing and result delivery.
- Mail the sample: Place the sealed tube and completed form in the provided envelope and mail it promptly. Most samples should be mailed within 24-48 hours of collection for best results.
Collect your sample from a regular bowel movement. Avoid collection if you have visible bleeding from hemorrhoids, are menstruating, or have a urinary tract infection, as these can affect results. The best time to mail your sample is on a Monday through Wednesday to avoid weekend delays. Store the completed sample at room temperature until mailing - do not refrigerate or freeze.
When Not to Collect a Sample
There are certain situations when you should delay sample collection to avoid potentially inaccurate results. Do not collect a sample if you have visible bleeding from hemorrhoids, as this can cause a false positive result. Women should avoid collection during menstruation and for three days afterward. Those with active urinary tract infections should wait until the infection is treated.
If you have recently had a colonoscopy, rectal examination, or any procedure involving the rectum, wait at least one week before collecting a sample. Similarly, if you have had diarrhea or gastrointestinal illness, wait until normal bowel movements resume. These precautions help ensure the test accurately reflects conditions in your colon rather than temporary or external factors.
What Do FIT Test Results Mean?
A negative FIT result means no blood was detected in your stool sample, indicating a lower likelihood of colorectal cancer. A positive result means blood was detected and requires follow-up colonoscopy to determine the cause - but most positive results are NOT caused by cancer.
Understanding your test results is crucial for taking appropriate next steps. The FIT test is designed as a screening tool to identify individuals who may benefit from further investigation. It is important to remember that the test detects blood, not cancer directly, and there are many benign reasons for blood in the stool.
Negative Result
A negative result indicates that no significant amount of blood was detected in your stool sample. This is reassuring, but it does not guarantee the absence of polyps or cancer. Some polyps and early cancers do not bleed, or may bleed intermittently, potentially being missed on a single test. This is why annual testing is so important - regular screening increases the chances of detecting any developing problems.
If your result is negative, you should plan to repeat the FIT test in one year. Maintaining this annual schedule is essential for the screening program to be effective. Studies show that the cumulative benefit of regular screening is significantly greater than single or sporadic testing.
Positive Result
A positive FIT result means that blood was detected in your stool sample. This does NOT mean you have cancer. In fact, among people with positive FIT results who undergo colonoscopy, only about 3-5% are found to have colorectal cancer. The majority of positive results are caused by other conditions.
Common causes of positive FIT results include hemorrhoids, which are swollen blood vessels in the rectum that frequently bleed, adenomatous polyps that may bleed but are not yet cancerous, anal fissures or small tears in the anal tissue, and inflammatory conditions of the colon. These conditions, while not cancer, may still require evaluation and treatment.
A positive result always requires follow-up with colonoscopy to determine the cause of the bleeding. Colonoscopy allows direct visualization of the entire colon and rectum, and enables the removal of any polyps found during the procedure. This is a critical step - delaying or avoiding colonoscopy after a positive FIT test removes the protective benefit of screening.
If your FIT test is positive, it is essential to follow up with colonoscopy as recommended by your healthcare provider. While most positive results are not cancer, the only way to know for certain is through colonoscopy. Early detection of cancer or precancerous polyps can be life-saving. Do not delay or repeat the FIT test instead of getting colonoscopy.
How Accurate Is the FIT Test?
The FIT test has a sensitivity of 74-79% for detecting colorectal cancer, meaning it correctly identifies about 3 out of 4 cancers. For advanced adenomas (precancerous polyps), sensitivity is 24-28%. When performed annually, the cumulative detection rate is significantly higher.
Understanding the accuracy of any screening test requires knowledge of two key concepts: sensitivity and specificity. Sensitivity refers to the test's ability to correctly identify those who have the disease (true positive rate), while specificity refers to its ability to correctly identify those without the disease (true negative rate).
For colorectal cancer detection, the FIT test demonstrates strong performance. Studies consistently show sensitivity ranging from 74-79% for detecting colorectal cancer when a single test is performed. This means that if 100 people with colorectal cancer were tested, approximately 74-79 would receive a positive result. The remaining 21-26 would receive a false negative result.
The specificity of the FIT test is approximately 94-96%, meaning that among people without colorectal cancer, about 94-96% will correctly receive a negative result. The remaining 4-6% will receive a false positive result, requiring colonoscopy that will not find cancer. While inconvenient, this follow-up investigation is still valuable as it may detect polyps or other conditions.
Detection of Precancerous Polyps
The FIT test is less sensitive for detecting advanced adenomas (precancerous polyps) than for detecting established cancer. Sensitivity for advanced adenomas ranges from 24-28%, meaning most precancerous polyps will not be detected by a single FIT test. This is because polyps bleed less frequently and less extensively than cancers.
However, this limitation is addressed through annual testing. Polyps that are not detected one year may be detected the following year as they grow and are more likely to bleed. Over time, annual FIT testing provides cumulative protection that significantly reduces both the incidence of colorectal cancer and mortality from the disease.
Factors Affecting Test Performance
Several factors can influence the accuracy of FIT test results. Sample handling is important - samples that are exposed to extreme temperatures or that take too long to reach the laboratory may yield less reliable results. Following collection and mailing instructions carefully helps ensure accurate results.
Certain medications may affect test results, although the FIT test is less affected by medications than older guaiac-based tests. Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) can cause gastrointestinal bleeding that may affect results. Anticoagulant medications may increase the likelihood of bleeding from any source. Discuss your medications with your healthcare provider if you have concerns.
What Happens After Follow-Up Colonoscopy?
Following colonoscopy for a positive FIT result, your healthcare provider will recommend ongoing surveillance based on findings. If polyps were removed, repeat colonoscopy may be needed in 3-5 years. If no abnormalities are found, you may return to regular FIT screening after an appropriate interval.
The colonoscopy performed after a positive FIT test serves both diagnostic and therapeutic purposes. During the procedure, the gastroenterologist examines the entire colon and rectum using a flexible camera, looking for polyps, cancers, or other abnormalities. If polyps are found, they can usually be removed during the same procedure, a process called polypectomy.
Following colonoscopy, your healthcare provider will discuss the findings and recommend appropriate follow-up. The recommendations depend entirely on what was found during the examination. If the colonoscopy shows no abnormalities (a "normal" or "negative" colonoscopy), you may return to regular FIT screening after an appropriate interval, typically after one year or as recommended by your provider.
If Polyps Were Found and Removed
Adenomatous polyps (adenomas) are precancerous growths that have the potential to develop into cancer over time. If adenomas are found and removed during colonoscopy, surveillance colonoscopy is recommended at intervals determined by the number, size, and type of polyps found. Generally, those with low-risk adenomas may need repeat colonoscopy in 5-10 years, while those with high-risk findings may need repeat examination in 3 years.
Hyperplastic polyps, another common type, are generally not considered precancerous and typically do not require shortened surveillance intervals. Your gastroenterologist will explain the specific type of polyps found and what they mean for your ongoing care.
If Cancer Is Diagnosed
If colonoscopy reveals colorectal cancer, your healthcare team will arrange additional tests to determine the stage of the cancer and plan appropriate treatment. Treatment may include surgery, chemotherapy, radiation therapy, or combinations of these approaches, depending on the cancer's location and stage.
The good news is that colorectal cancers detected through screening are more likely to be found at early stages when treatment is most effective. Five-year survival rates for localized colorectal cancer (cancer that has not spread beyond the colon or rectum) exceed 90%, emphasizing the life-saving potential of screening.
Can Colorectal Cancer Be Prevented?
While not all colorectal cancers can be prevented, regular screening can detect and remove precancerous polyps before they become cancer. Additionally, lifestyle factors including diet, physical activity, maintaining healthy weight, limiting alcohol, and not smoking can reduce colorectal cancer risk.
Colorectal cancer prevention occurs on two levels: primary prevention through lifestyle modifications that reduce the risk of developing polyps and cancer, and secondary prevention through screening that detects and removes precancerous growths before they become cancer.
The removal of adenomatous polyps during colonoscopy represents one of the most effective cancer prevention strategies available. Studies show that removing adenomas reduces colorectal cancer incidence by approximately 75-90% compared to leaving them in place. This is why follow-up colonoscopy after positive FIT tests is so important.
Lifestyle Factors That Reduce Risk
Several modifiable lifestyle factors are associated with reduced colorectal cancer risk. A diet high in fiber from fruits, vegetables, and whole grains appears protective, while diets high in processed and red meat are associated with increased risk. The mechanisms involve both direct effects on the bowel lining and influences on the gut microbiome.
Regular physical activity is consistently associated with lower colorectal cancer risk. Current recommendations suggest at least 150 minutes of moderate-intensity activity or 75 minutes of vigorous activity per week. Maintaining a healthy body weight is also important, as obesity increases colorectal cancer risk.
Limiting alcohol consumption and avoiding tobacco use provide additional protection. Alcohol is a known carcinogen that increases colorectal cancer risk in a dose-dependent manner. Smoking is associated with increased risk of developing and dying from colorectal cancer, with the risk increasing with duration and amount of tobacco use.
- High-fiber diet: Fruits, vegetables, whole grains, and legumes
- Regular physical activity: At least 150 minutes moderate activity per week
- Healthy weight: Maintain body mass index in normal range
- Limit processed meat: Reduce consumption of processed and red meat
- Limit alcohol: If you drink, do so in moderation
- Don't smoke: Avoid tobacco in all forms
Frequently Asked Questions About Colorectal Cancer Screening
The FIT test (Fecal Immunochemical Test) is a screening test that detects hidden blood in stool, which can be an early sign of colorectal cancer or precancerous polyps. It uses antibodies to detect human hemoglobin specifically, making it more accurate than older guaiac-based tests. The test is done at home using a simple collection kit, and samples are mailed to a laboratory for analysis. No dietary restrictions or bowel preparation are needed.
The FIT test has a sensitivity of 74-79% for detecting colorectal cancer, meaning it correctly identifies about 3 out of 4 colorectal cancers. For advanced adenomas (precancerous polyps), sensitivity is 24-28%. When performed annually as recommended, the cumulative detection rate is significantly higher. The specificity is approximately 94-96%, meaning most people without cancer correctly receive negative results.
Most guidelines recommend starting colorectal cancer screening at age 45 for people at average risk, continuing through age 75. This represents a change from older recommendations that suggested starting at age 50, reflecting increasing rates of colorectal cancer in younger adults. Those with increased risk factors such as family history of colorectal cancer, inflammatory bowel disease, or genetic syndromes may need to start screening earlier and should discuss personalized plans with their healthcare provider.
The FIT test should be done annually (once per year) for optimal effectiveness. Regular yearly testing is important because the test detects blood that may be present intermittently, and cancers may develop between tests. Maintaining consistent annual screening provides much better protection than sporadic testing. Many organized screening programs send invitations and kits to eligible adults to help maintain this schedule.
A positive FIT test means blood was detected in your stool sample. This does NOT automatically mean you have cancer - only about 3-5% of people with positive FIT tests are found to have colorectal cancer upon follow-up. However, a positive result requires colonoscopy examination to determine the cause. Common causes include polyps (which can be removed during colonoscopy), hemorrhoids, and inflammation. It is essential to follow up promptly with colonoscopy as recommended.
No, you do not need to change your diet before the FIT test. Unlike older guaiac-based stool tests, the FIT test specifically detects human blood and is not affected by foods like red meat or certain vegetables. You can eat normally before and during sample collection. Most medications can also be continued, though you should discuss any concerns with your healthcare provider, particularly if you take blood thinners or aspirin.
References and Sources
This article is based on current international medical guidelines and peer-reviewed research. All medical claims are supported by Level 1A evidence from systematic reviews and randomized controlled trials.
- US Preventive Services Task Force. Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;325(19):1965-1977. doi:10.1001/jama.2021.6238
- Shaukat A, Kahi CJ, Burke CA, et al. ACG Clinical Guidelines: Colorectal Cancer Screening 2021. Am J Gastroenterol. 2021;116(3):458-479.
- European Society of Gastrointestinal Endoscopy (ESGE). Quality in screening colonoscopy and FIT-based colorectal cancer screening programmes. Endoscopy. 2023.
- Cochrane Database of Systematic Reviews. Screening for colorectal cancer using the faecal immunochemical test (FIT). 2023.
- World Health Organization. WHO Guide to Cancer Early Diagnosis. Geneva: World Health Organization; 2023.
- Rex DK, Boland CR, Dominitz JA, et al. Colorectal Cancer Screening: Recommendations for Physicians and Patients from the U.S. Multi-Society Task Force on Colorectal Cancer. Am J Gastroenterol. 2024.
- Imperiale TF, Ransohoff DF, Itzkowitz SH, et al. Multitarget Stool DNA Testing for Colorectal-Cancer Screening. N Engl J Med. 2014;370:1287-1297.
About Our Medical Editorial Team
This article was written and reviewed by the iMedic Medical Editorial Team, which consists of licensed specialist physicians with expertise in gastroenterology, oncology, and preventive medicine. Our team follows international guidelines including WHO, USMSTF, and ESGE recommendations, and adheres to the GRADE evidence framework for all medical content.
All content undergoes rigorous review by board-certified physicians before publication. We verify all claims against current peer-reviewed literature and update articles when new evidence emerges.
We prioritize Level 1A evidence from systematic reviews and meta-analyses. Our content follows GRADE methodology and cites sources from major medical organizations and peer-reviewed journals.
Conflict of Interest Statement: The iMedic Medical Editorial Team has no financial relationships with pharmaceutical companies, device manufacturers, or other commercial entities that could create conflicts of interest in our medical content.