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Occult blood
Test CodeOCBL
Alias/See Also
Guaiac Test, Occult Blood Stool, Hemoccult, Guaiac Stool, Stool Guaiac, Stool Occult Blood
Preferred Specimen
Stool (small amount)
Instructions
• For seven days before and during the stool collection avoid non-steroidal anti-inflammatory drugs such as ibuprofen, naproxen, or more than one adult aspirin a day.
• For three days before and during the stool collection period avoid vitamin C in excess of 250 mg a day and red meat. Eat a well balance diet including fiber such as bran cereals fruits and vegetables.
• A small fecal specimen, three serial fecal specimens are recommended when screening asymptomatic patients.
• Avoid contact with toilet bowl water.
• Do not collect specimens during a menstrual period, or while experiencing bleeding hemorrhoids or blood in the urine.
Occult Blood using Hemoccult- SENSA cards
• For three days before and during the stool collection period avoid vitamin C in excess of 250 mg a day and red meat. Eat a well balance diet including fiber such as bran cereals fruits and vegetables.
• A small fecal specimen, three serial fecal specimens are recommended when screening asymptomatic patients.
• Avoid contact with toilet bowl water.
• Do not collect specimens during a menstrual period, or while experiencing bleeding hemorrhoids or blood in the urine.
Occult Blood using Hemoccult- SENSA cards
- Patient prepares Hemoccult card by recording full name, date and time of specimen collection.
- Raw stool specimen is collected into a sterile urine cup.
- Place card on a clean surface and open the flap.
- Dip applicator stick and take a small portion of the stool sample and apply a thin smear inside Box 'A'.
- Reuse applicator stick to obtain second sample from a different part of stool. Apply inside Box 'B'.
- Close flap and place card in a sealed zip-lock bag. Return card to the Laboratory for testing.
- If the order is for stool specimens times three to be collected on 3 consecutive days, then store cards at room temperature before dropping them off at the Laboratory.
Transport Container
Clean specimen container. An inoculated Hemocult Slide is acceptable.
Specimen Stability
Room temperature: 14 days, Refrigerated: unacceptable, Frozen: unacceptable
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Stool with visible blood.
Methodology
Oxidation of guaiac
Limitations
• Bowel lesions, including some polyps and colorectal cancers, may not bleed at all or may bleed intermittently. Also, blood, if present, may not be distributed uniformly in the fecal specimen. Consequently, a test result may be negative even when disease is present.
• Conversely, a test result may be positive on specimens from healthy patients. This may be due to interfering substances in the diet or to medications. It may also be due to low but detectable levels of blood loss, common to both healthy adults and patients with gastrointestinal disease.
• Therefore, results with this test cannot be considered conclusive evidence of the presence or absence of gastrointestinal bleeding or pathology. This test is designed for preliminary screening as an aid to diagnosis. It is not intended to replace other diagnostic procedures such as sigmoidoscopy, colonoscopy, barium enema, or other x-ray studies.
• Fecal occult blood tests, should not be used to test gastric specimens. Interfering factors, such as low pH, high drug concentrations, metal ions or plant peroxidase in food may affect the function of guiac-based occult blood tests.
• Conversely, a test result may be positive on specimens from healthy patients. This may be due to interfering substances in the diet or to medications. It may also be due to low but detectable levels of blood loss, common to both healthy adults and patients with gastrointestinal disease.
• Therefore, results with this test cannot be considered conclusive evidence of the presence or absence of gastrointestinal bleeding or pathology. This test is designed for preliminary screening as an aid to diagnosis. It is not intended to replace other diagnostic procedures such as sigmoidoscopy, colonoscopy, barium enema, or other x-ray studies.
• Fecal occult blood tests, should not be used to test gastric specimens. Interfering factors, such as low pH, high drug concentrations, metal ions or plant peroxidase in food may affect the function of guiac-based occult blood tests.
Reference Range
Negative
Clinical Significance
This is a test for detecting fecal occult blood which may be indicative of gastrointestinal diseases. It is not a test for colorectal cancer or any other specific diseases.
