What is the Fecal Occult Blood Test (FOBT)?
A Fecal Occult Blood Test (FOBT) is a screening test used to detect hidden (occult) blood in the stool that cannot be seen with the naked eye. Small amounts of blood in the stool may be an early sign of colorectal cancer, colon polyps, or other conditions affecting the digestive tract. Since bleeding is often intermittent and not visible, the test helps identify blood that might otherwise go unnoticed.
The Fecal Occult Blood Test (FOBT) is commonly used as a screening test for colorectal cancer in people who do not have symptoms. It may also be advisable to investigate unexplained gastrointestinal bleeding or iron-deficiency anaemia. There are different types of FOBTs, including the guaiac fecal occult blood test (gFOBT) and the fecal immunochemical test (FIT). Depending on the type of test used, dietary or medication restrictions may apply before sample collection. If blood is detected, additional tests such as a colonoscopy are usually recommended to determine the cause.
How is the Test Performed?
Preparation
- Preparing for a Fecal Occult Blood Test (FOBT) depends on the type of test being performed.
- Follow your healthcare provider’s instructions carefully before collecting the sample.
- For a guaiac FOBT (gFOBT), you may be asked to avoid certain foods, vitamin C supplements, and some medications for several days before testing.
- For a fecal immunochemical test (FIT), dietary restrictions are generally not required.
- Avoid collecting the sample during menstrual bleeding or when bleeding from haemorrhoids or the urinary tract may contaminate the specimen.
Collection
- The test requires a stool sample, which is usually collected at home.
- Use the collection kit or sterile container provided by the laboratory.
- Prevent the stool sample from mixing with urine or toilet water.
- Collect the required amount of stool following the instructions provided with the kit.
- Some types of FOBTs require samples from multiple bowel movements.
- Return the sample to the laboratory as instructed.
Lab Analysis
The stool sample is analysed to detect the presence of occult (hidden) blood. Depending on the testing method, the laboratory uses either a chemical reaction (gFOBT) or an antibody-based method (FIT) to identify blood in the stool. A positive result indicates that blood has been detected but does not identify the source of bleeding. Your healthcare provider will interpret the results alongside your medical history, symptoms, and risk factors, and may recommend additional investigations if necessary.
What are the symptoms that Prompt this Test?
A Fecal Occult Blood Test (FOBT) is commonly used as a screening test for colorectal cancer in people who do not have symptoms. It may also be recommended if your healthcare provider suspects bleeding somewhere in the digestive tract or wants to investigate unexplained anaemia or gastrointestinal symptoms.
Screening for Colorectal Cancer
Your healthcare provider may recommend a Fecal Occult Blood Test (FOBT) if you:
- Are of screening age for colorectal cancer (likely at age 45)
- Have an increased risk of colorectal cancer
- Have a family history of colorectal cancer or colon polyps
- Need routine colorectal cancer screening despite having no symptoms
Symptoms That May Prompt This Test
A Fecal Occult Blood Test (FOBT) may also be recommended if you experience:
- Blood in the stool that is not visible to the naked eye
- Iron deficiency anaemia
- Persistent fatigue or weakness related to unexplained blood loss
- Changes in bowel habits, such as persistent diarrhoea or constipation
- Abdominal pain or cramping
- Unexplained weight loss
- Persistent gastrointestinal discomfort
Your healthcare provider may use the test together with other investigations to identify the cause of bleeding within the digestive tract.
What are Normal Ranges for This Test?
There’s no numerical value for Fecal Occult Blood Test (FBOT) normal range. Results are reported based on whether hidden blood is detected in the stool.
Common interpretations include:
Negative: No occult (hidden) blood is detected in the stool. This is considered the normal result.
Positive: Occult blood is detected in the stool, indicating that further evaluation may be required.
A positive FOBT does not necessarily mean colorectal cancer is present. Hidden blood may also result from conditions such as colon polyps, haemorrhoids, ulcers, inflammatory bowel disease, or other gastrointestinal disorders.
“The reference ranges vary depending on the laboratory and the methodology used. Individuals must consult their healthcare provider for correct interpretation of the results.”
What Happens if Test Results Show Abnormal Findings?
A positive Fecal Occult Blood Test (FOBT) indicates that hidden blood has been detected in the stool. However, the test does not identify the source or cause of the bleeding. Additional investigations are needed to determine why blood is present.
Positive FOBT
A positive result may be associated with:
- Colorectal cancer
- Colon polyps
- Haemorrhoids
- Stomach or intestinal ulcers
- Inflammatory bowel disease (IBD)
- Diverticular disease
- Bleeding from another part of the digestive tract
If the test is positive, your healthcare provider will usually recommend a colonoscopy to examine the colon and identify the source of the bleeding.
Negative FOBT
A negative result means no hidden blood was detected in the stool sample at the time of testing. However, it does not completely rule out colorectal cancer or other gastrointestinal conditions because some lesions may bleed intermittently.
If symptoms persist despite a negative result, your healthcare provider may recommend repeat testing or additional investigations, such as a colonoscopy, depending on your age, medical history, family history, and overall risk factors.
Need a Fecal Occult Blood Test (FOBT)? Book your appointment today for reliable colorectal cancer screening and comprehensive digestive health assessment.
