I. Overview of the Fecal Immunochemical Test and Fecal Occult Blood Test

Why should I get tested?

The purpose of the fecal immunochemical test and the fecal occult blood test is to detect blood in the stool. If blood is present in a stool sample, a health care provider can order additional tests to help determine if the individual has colon cancer or another medical condition that needs to be treated. Early detection of colon cancer is important, as it may be easier to treat in its early stages. Once the cancer grows and spreads, it becomes more difficult to treat. Therefore, early detection saves lives.

When should I get tested?

According to guidelines developed by the National Cancer Institute, men and women should have a fecal immunochemical test or a fecal occult blood test every year, starting at the age of 50.

What is required for the test?

Both tests require an individual to provide a stool sample, which can be collected at home and mailed to or dropped off at the laboratory. The fecal immunochemical test typically requires samples from two or three different bowel movements, while the fecal occult blood test requires samples from three bowel movements.

What do I need to do to prepare for the test?

The preparation required depends on which test is being used. Some foods and medications can affect the results of the fecal occult blood test, which checks for heme in the stool. Heme is part of hemoglobin, a protein found in red blood cells. Some foods contain heme, which means the individual must avoid beef, pork, lamb, and other meats for at least three days before collecting samples for the fecal occult blood test. Vitamin C can also affect the results of this test, making it necessary to refrain from consuming more than 250 mg of vitamin C per day for at least seven days before collecting stool samples. This includes vitamin C from foods, beverages, and supplements. The fecal immunochemical test detects the whole hemoglobin protein, so it’s not necessary to make any dietary adjustments before collecting stool samples.

Some health care providers also recommend that their patients stop taking ibuprofen, naproxen, and other nonsteroidal anti-inflammatory drugs seven days before doing the fecal occult blood test. These medications can irritate the gastrointestinal system, resulting in a positive result on the fecal occult blood test, even if the individual doesn’t have colon cancer or another medical condition that causes GI bleeding.

II. The Basics of Colon Cancer

Colon cancer develops when cells in the lower part of the large intestine start multiplying rapidly. As these cells continue to divide, they can form tumors inside the colon. Instead of dying, damaged cells remain in the colon, further interrupting the normal process of cell development. Several factors increase the likelihood that someone will develop colon cancer. Some of these factors relate to an individual’s health history and family medical history. For example, someone with ulcerative colitis or Crohn’s disease has an elevated risk of developing colon cancer. A family history of colon cancer or polyps is also a risk factor for colon cancer, as is Lynch syndrome, a genetic disorder that increases a person’s likelihood of developing colon cancer.

Some of the risk factors for colon cancer have to do with an individual’s lifestyle. Tobacco use and excessive alcohol consumption increase the risk of developing colon cancer. So do living a sedentary lifestyle, eating a diet high in fat or low in fiber, not eating enough fruits and vegetables, and obesity.

In its early stages, colon cancer may not cause any obvious symptoms, which is why it’s so important to have screening tests such as the fecal immunochemical test or the fecal occult blood test. One possible sign of colon cancer is losing weight without trying. Blood in the stool, persistent stomach pain, and stomach cramps are also signs of colon cancer.

III. How the Fecal Immunochemical Test and Fecal Occult Blood Test Work

The fecal immunochemical test and fecal occult blood test are similar, but they have slightly different requirements for sample collection. Each test comes in a kit with detailed directions and all the supplies needed to collect the required number of stool samples. For the fecal immunochemical test, the kit usually contains a brush or other device to collect samples from the toilet. Once the sample is collected, the collection device is brushed onto a test card. The cards must be labeled according to the directions in the kit before they’re mailed to a laboratory or medical facility.

For the fecal occult blood test, stool should be collected and stored in a container. The test kit should contain an applicator that can be used to smear some of the stool on a test card. As with the fecal immunochemical test, all samples should be labeled according to the instructions in the kit. The sample cards are then mailed to a laboratory or medical facility. Test kits are made by several companies, so it’s important to follow the instructions that come with the kit to ensure accurate results.

Both tests check for the presence of blood in the stool that can’t be seen with the naked eye. Each test has several advantages, but there are also some disadvantages to this type of colon cancer screening. One of the main benefits of the fecal immunochemical test and the fecal occult blood test is that they are noninvasive. Stool samples can be collected at home, reducing the embarrassment that some people feel when they are screened for colon cancer. Both tests are also less expensive than other screening methods for colon cancer.

One of the main disadvantages of these tests is that they can produce a positive result even if the individual doesn’t have colon cancer, resulting in the need for additional screening, which is invasive and may be costly. Another disadvantage is that the fecal immunochemical test and fecal occult blood test can’t diagnose every case of colon cancer.

IV. Treatment for Colon Cancer

Treatment options for colon cancer include surgery, cryosurgery, radiation therapy, targeted therapy, immunotherapy, chemotherapy, and radiofrequency ablation. The type of treatment used depends on several factors, including how advanced the cancer is, so it’s important to work closely with an oncologist to determine which treatment is likely to yield the best chance of success.

Surgery

Surgery involves surgical removal of the cancer, whether by local excision or resection of the colon. Local excision is a procedure in which the doctor inserts an instrument into the colon via the rectum; the instrument is used to cut out the cancer. If the tumor is too large for a local excision, the surgeon performs a colon resection, which entails removing the part of the colon that contains the cancer. Once the cancerous portion is removed, the remaining pieces of the colon are sutured together.

Cryosurgery and Radiation Therapy

Cryosurgery, or cryotherapy, uses a specialized instrument to freeze the cancerous tissue in the colon. Freezing kills the tissue so that the cancer cells don’t continue to grow. Radiation therapy uses high-dose radiation to destroy cancer cells or prevent them from continuing to multiply. In some cases, a machine is placed outside the body so that radiation can be directed at the location of the cancer. This is known as external radiation therapy. In other cases, a radioactive substance is placed in a “seed,” catheter, or other device and inserted directly into the affected area of the colon. This is known as internal radiation therapy.

Targeted Therapy

Targeted therapy is used to destroy cancer cells without damaging the healthy cells nearby, which can reduce the risk of serious side effects. Monoclonal antibodies have the ability to identify substances that promote the growth of cancer cells. These antibodies attach to the cancer cells and kill them, prevent them from spreading to other parts of the body, or prevent them from continuing to divide. Angiogenesis inhibitors prevent new blood vessels from growing, which reduces the blood supply to a tumor. Without adequate blood flow, the tumor can’t continue growing.

Immunotherapy

Immunotherapy enhances the immune system’s ability to fight colon cancer. A common type of immunotherapy for colon cancer is immune checkpoint inhibitor therapy. In people with cancer, a substance called PD-1 attaches to a substance called PDL-1, which is found on cancer cells. When PD-1 attaches to PDL-1, it prevents the immune system from destroying the cancer cell. Immune checkpoint inhibitor therapy prevents PD-1 from binding with PDL-1, allowing the immune system to kill cancerous cells.

Chemotherapy and Radiofrequency Ablation

Chemotherapy is a cancer treatment that uses medications to destroy cancer cells or prevent them from multiplying. These medications can be given orally or intravenously. Systemic chemotherapy refers to chemotherapy that’s introduced to the bloodstream, allowing the medication to kill cancer cells in many parts of the body. Regional chemotherapy is administered directly to a specific organ or body cavity, targeting the cancer cells in that particular region. Radiofrequency ablation is a procedure in which a probe is introduced to the cancerous area. The probe produces an electrical current that can destroy cancer cells.

V. FAQs

If my fecal test is negative, does that mean I don't have colon cancer?

Not necessarily. The fecal immunochemical test and fecal occult blood test can only detect blood that is present in stool samples from two or three bowel movements. It’s possible to have colon cancer without having blood in the stool.

If my fecal test is positive, do I definitely have colon cancer?

No. Colon cancer is just one possible cause of blood in the stool. Other medical conditions, such as hemorrhoids and bleeding ulcers, can also cause bloody bowel movements. With the fecal occult blood test, it’s also possible to get a positive result from eating red meat, consuming more than 250 mg of vitamin C per day, or taking NSAIDs within several days of collecting the stool samples.

Is one fecal test better than the other?

Both fecal tests are inexpensive and noninvasive. The only major difference between them is that no special preparation is required for the fecal immunochemical test, while the fecal occult blood test requires some dietary restrictions and medication adjustments. Thus, the fecal immunochemical test is slightly more convenient.

What additional tests will I need if my fecal immunochemical test or fecal occult blood test comes back positive?

Anyone with a positive fecal immunochemical test or fecal occult blood test should have a colonoscopy, a procedure in which a scope is inserted into the lower part of the large intestine. The scope has a camera attached to it, allowing a physician to check the inside of the colon for polyps, tumors, and other signs of colon cancer. A colonoscopy can help identify the source of the blood and guide health care providers in making treatment decisions.

Is it possible to prevent colon cancer?

Some risk factors for colon cancer are not modifiable, which means they can’t be changed. For example, someone who has a family history of colon cancer can’t change the fact that at least one relative had colon cancer at some point. Some factors, however, are modifiable. These factors include dietary habits, activity level, and tobacco use. The American Society of Colon and Rectal Surgeons recommends eating a high-fiber diet that is low in animal fat, exercising regularly, and avoiding tobacco products. Eating plenty of fruits and vegetables can also reduce a person’s risk of developing colon cancer.

VI. Additional Resources

To learn more about colon cancer and testing for this condition, use the following resources.

NameWebsiteSummary
American Cancer Societywww.cancer.org/The American Cancer Society provides in-depth information on many types of cancer, including colon cancer.
American Society of Colon and Rectal Surgeonswww.fascrs.org/Access the ASCRS patient library, which includes information on colon cancer and other conditions of the colon and rectum.
Dana-Farber Cancer Institutewww.dana-farber.org/Learn how to reduce the risk of colon cancer by making healthy dietary choices.
MedlinePlusmedlineplus.gov/MedlinePlus provides information on the screening tests used to diagnose colon cancer.
Colon Cancer Coalitioncoloncancercoalition.org/The Colon Cancer Coalition explains what colon cancer is and how it can be prevented.

VII. Sources Used in This Article