Collecting Stool Specimen

What It Is

You gather a sample of feces for lab analysis. Done right, it detects pathogens, blood, fat, parasites, and other abnormalities, and tells you a lot about the patient's digestive health.

Indications

• Diagnosing GI infections from bacteria, viruses, or parasites
• Detecting occult (hidden) blood, which can point to colorectal cancer or other GI bleeding
• Assessing malabsorption disorders like celiac disease or chronic pancreatitis
• Identifying inflammatory bowel disease (IBD) or irritable bowel syndrome (IBS)
• Monitoring how well treatment is working for a GI condition

Fecal Occult Blood Testing (FOBT)

FOBT detects hidden blood in the stool, a sign of GI bleeding that can come from colorectal cancer, polyps, ulcers, or inflammatory bowel disease. It is a common colorectal cancer screen. Major guidelines now recommend most adults at average risk begin screening at age 45, sooner for those with a family history or other risk factors (USPSTF; CDC).

Types

1. Guaiac-based FOBT (gFOBT). Uses guaiac to detect heme, a component of hemoglobin. You smear a small stool sample on a test card and apply developer solution. If blood is present, the guaiac turns blue.
2. Immunochemical FOBT (iFOBT or FIT). Uses antibodies to detect the globin part of human hemoglobin. The patient collects a small sample with a special device that goes to the lab.
3. Fecal DNA test. Looks for DNA mutations from cancer cells or precancerous polyps, and includes an immunochemical test for hemoglobin.

How to Collect

Assessment

1. Patient history. Symptoms, diet, and any medications that could affect the sample.
2. Indication. Know why you are collecting (infection, occult blood, malabsorption). It shapes the method.
3. Patient ability. Can they collect it themselves, or do they need help?

Planning

Pick the right lab-provided container, time the collection to avoid dietary or medication interference, and teach the patient why technique matters.

Delegation. UAP can handle random stool collections. The nurse handles stool cultures with sterile swabs.

Preparation. Walk the patient through:

• Dietary restrictions. Avoid foods and drugs that skew results: red meat, beets, NSAIDs, and vitamin C supplements.
• Hygiene. Clean the genital area so urine or menstrual blood does not contaminate the sample.
• Collection kit. Usually a sterile container, scoop or spatula, plastic wrap or liner, gloves, labels, and a biohazard bag.

Implementation

1. Wash your hands with soap and water before you start.
2. Open the collection container from the kit so it is ready.
3. Pass stool into a clean, dry container, like a bedpan or a plastic collection device over the toilet seat, so it does not mix with toilet water.
4. Transfer a small amount with the scoop or spatula, staying under the fill line. Enough to test, not so much it leaks.
5. Close the lid securely to prevent leakage and contamination.
6. Label with the patient's name, date, and time. Typically you collect three specimens from different bowel movements on consecutive days, each dated.
7. Store cool or refrigerate if instructed, to preserve the sample.
8. Wash your hands after handling the sample.
9. Get it to the lab as soon as possible for timely, accurate results.

Nursing Considerations

Teach the patient how to collect, handle, and store the sample, and why timing matters. Watch for the things that wreck results:

1. Certain foods (red meat, raw vegetables) cause false positives on occult blood tests. They carry peroxidase enzymes or heme that mimic blood.
2. NSAIDs or aspirin can cause GI bleeding and a false positive unrelated to what you are testing for.
3. Contamination with urine, menstrual blood, or toilet water skews results by introducing foreign substances or microbes.
4. Improper storage lets the sample degrade. The wrong temperature allows bacterial growth or chemical changes that make it unreliable.
5. No toilet tissue in the bedpan after defecation. Tissue chemicals interfere with detecting blood or pathogens, and fibers contaminate the sample.
6. Remove toilet bowl cleaners and flush the toilet twice before the test, so chemicals do not contaminate the sample.

Frequently Asked Questions

What does a stool specimen test for? It screens for GI infections (bacteria, viruses, parasites), occult blood that can point to colorectal cancer or other bleeding, malabsorption disorders, and inflammatory bowel disease, and it tracks how well treatment for a GI condition is working.

At what age should colorectal cancer screening start? Major guidelines now recommend most adults at average risk begin at age 45, earlier with a family history or other risk factors. Stool-based options like FIT are done annually (USPSTF; CDC).

What is the difference between gFOBT and FIT? Guaiac-based FOBT (gFOBT) uses a chemical reaction to detect heme and requires dietary restrictions beforehand. The fecal immunochemical test (FIT) uses antibodies specific to human hemoglobin, needs no diet changes, and is the more common choice today.

Why does the patient avoid red meat and NSAIDs before an occult blood test? Red meat and some raw vegetables carry heme or peroxidase that mimic blood, and NSAIDs or aspirin can cause GI bleeding unrelated to the disease being screened. Both produce false positives on guaiac-based tests.

How many samples are needed? For occult blood screening you typically collect three specimens from separate bowel movements on consecutive days, each labeled with the date and time, then get them to the lab promptly.

Can a stool sample be contaminated? Yes. Urine, menstrual blood, toilet water, toilet tissue, and bowl cleaners all skew results. Pass stool into a clean dry container, keep tissue out of the bedpan, and flush twice to clear any chemicals before collecting.