Specimen Collection

Occult Blood, Feces

Occult Blood (Guaiac) Test - Feces Samples

  1. Patient Preparation - Collection cards for this test are usually given tot eh patient at the Clinic location. It is recommended to collect three specimens over three days or three different bowel movements in order to detect occult blood in the patient's samples.
  2. It is recommended that the patient be placed on a high residue diet starting 2 days before and continuing through the test period.
  3. Diet may include:
    1. Meats: Only small amounts of chicken, turkey and tuna.
    2. Vegetables: Generous amounts of both raw and cooked vegetables including lettuce, corn, spinach, carrots and celery. Avoid those with high peroxidase activity.
    3. Fruits: Plenty of fruits, especially prunes and apples.
    4. Cereals: Bran and bran-containing cereals.
    5. Moderate amounts of peanuts and popcorn daily. If any of the above foods are known to cause discomfort, the patient is instructed to inform his physician.
  4. Foods to be avoided:
    1. Meat: Diet should not include any red or rare meat.
    2. Fruits and vegetables containing high peroxidase activity, such as Turnip, Broccoli, Horseradish, Cauliflower, Cantaloupe, and Parsnip.
  5. Other factors which affect the test:
    1. Medications: For 2 days prior to and during the testing, do not ingest aspirin or tonics or vitamin preparations which contain Vitamin C (ascorbic acid) in excess of 250 mg per day.
    2. Bleeding hemorrhoids.<
    3. Collection of specimen during menstrual-cycle.
    4. Improper specimen collection.
    5. Other diseases of gastrointestinal tract such as colitis, gastritis, diverticulitis and bleeding ulcers.
  6. Specimen Handling:
    1. It is important that the stool specimen be applied as a very thin smear to the ColoScreen Slides. The smears may be prepared and developed immediately or prepared and stored up to 12 days prior to development.
    2. Care should be taken so that anything coming into contact with the specimen is free of blood. Because of the non-homogeneity of the stool, it is recommended that the test be performed on three (3) consecutive evacuations.
  7. Interfering Substances:
    1. Ingestion of ascorbic acid (Vitamin C) in high doses has been shown to cause false negative results and intake should be discontinued 2 days to and during the test period.
    2. Peroxidase from fruit and vegetables can cause false positive results. Elimination of red meat from the diet during the test period eliminates the source of hemoglobin which can cause false positives.
    3. Oral medications (such as aspirin, indomethacin, etc.) and heavy alcohol consumption may cause irritation or bleeding of the gastrointestinal tract and should be discontinued for 2 days prior to and during the testing period.