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CLIA Complexity: Waived-Definitive




I.       Principle


The Hemoccult SENSA test is a qualitative method for detecting fecal occult blood.  The test is based on the oxidation of guaiac by hydrogen peroxide to a blue-colored compound.  The heme portion of hemoglobin, if present in the fecal sample, has peroxidase activity which catalyzes the oxidation of alpha guaiaconic acid (active component of the guaiac paper) by hydrogen peroxidase (active component of the developer) to form a highly conjugated blue quinone compound.


This test is not a test for colorectal cancer or any other specific diseases.  It is recommended as a diagnostic aid during routine physical examinations, for hospital patients, to monitor for bleeding in patients with iron deficiency anemia or recuperating from surgery, peptic ulcer, ulcerative colitis and other conditions, and in screening programs for colorectal cancer when the Special Diagnostic Diet is closely followed.


II.      Specimen


The Hemoccult SENSA test requires only a small fecal sample.  Prior to collecting the patient’s sample, the patient’s identity must be verified by looking at the arm band.  The sample should be collected directly from a diaper or from the toilet bowl with the aid of a container and toilet tissue.  Since gastrointestinal lesions may be intermittent, fecal samples for testing should be collected from three consecutive bowel movements or three bowel movements closely spaced in time.  To further increase the probability of detecting occult blood, separate samples should be taken from two different sections of each fecal specimen.


The sample is applied as a thin smear using the applicator stick provided.  Hemoccult slides may be prepared and developed immediately or prepared and stored for up to 14 days at room temperature, 15-300 C before developing.  Fecal samples should not be collected if hematuria or obvious rectal bleeding, such as from hemorrhoids, is present.  Pre-menopausal women must be instructed to avoid collecting fecal samples during or in the first three days after a menstrual period.


The Special Diagnostic Diet is as follows:


Foods to eat:

Well-cooked pork, poultry, and fish

Any cooked fruits and vegetables

High fiber foods


Foods, Drugs, and Vitamins to Avoid:

Red meat, including processed meats and liver

Any raw fruits and vegetables

Vitamin C in excess of 250 mg per day

Aspirin or other non-steroid anti-inflammatory drugs (avoid for 7 days prior to and during the test period)





III.     Reagents and Supplies


1.       Materials


§         Hemoccult SENSA Slides contain a natural guaiac resin in standardized, high-quality filter paper.

§         Hemoccult SENSA Developer solution contains a stabilized mixture of less than 4.2% hydrogen peroxide, 84% denatured ethyl alcohol and enhancer in aqueous solution.

NOTE: Any lot number of developer may be used with any lot number of slides as long as both are within expiration date and are “color-matched.”

§         Applicator sticks


2.       Storage and Stability


§         Store product at room temperature 15-300C in original packaging.  Protect slides from heat and light.  Do not store near volatile chemicals (e.g., iodine, chlorine, bromine, or ammonia).  Do not use after expiration date which appears on each slide.

§         Do not refrigerate or freeze.

§         Protect Hemoccult Developer from heat and keep bottle tightly capped when not in use.  It is flammable and subject to evaporation.  Do not use after expiration date on bottle.

§         Guaiac Slides and Developer should be visually inspected before use for any discoloration or damage that might interfere with testing.


3.       Precautions


Because this test is visually read and requires color differentiation, it should not be interpreted by people who are color-blind or visually impaired.


Hemoccult Developer is an irritant and is flammable.  Avoid contact with eyes and skin.  If developer comes in contact with eyes or skin, rinse promptly with water.  Do not leave uncapped or expose to heat.


IV.     Procedure


1.       Properly fill out patient identification, collection date, and physician name in spaces provided on front of each slide.  This is especially important to do on slides that are not to be developed immediately.

2.       Collect small fecal sample on one end of applicator and apply thin smear inside Box A.

3.       Reuse applicator to obtain second sample from a different part of feces.  Apply thin smear inside Box B.

4.       Close cover.

5.       If testing immediately, wait 3-5 minutes before developing.   Otherwise, store slides as directed for up to 14 days until ready to develop.

6.       Developing the test:

1.       Open flap in back of slide and apply two drops of Developer to guaiac paper directly over each smear.

2.       Read results within 60 seconds. Any trace of blue on or at the edge of the smear is positive for occult blood.

7.       Record results appropriately on patient’s chart.


V.       Quality Control


The function and stability of the slides and developer can be tested using the on-slide Performance Monitor feature.  The positive (+) and negative (-) Performance Monitor areas are located under the sample windows on the developing side of the slides.  The Performance Monitor areas must be developed with each patient test.


The positive Performance Monitor area contains a hemoglobin-derived catalyst which will turn blue within 10 seconds after applying developer.  The negative Performance Monitor area contains no such catalyst and should not turn blue after applying developer.


The Performance Monitor feature provides assurance that the guaiac paper and developer are functional.  In the event that the Performance areas do not react as expected after applying developer, the test results should be regarded as invalid and unreportable.  The sample should then be retested on a new slide.


If the Quality Control Monitors do not perform as expected, follow the following troubleshooting steps:





Do not report the patient result


Check expiration dates of the quaiac slides and developer


Review the procedure


Repeat control monitors with a new slide and freshly opened developer


If successful, discard old vial of developer


Using a new slide repeat patient test and controls


If the controls do not perform correctly on repeat, call the manufacturer of Hemoccult at SmithKline Diagnostics, 1-800-877-6242.  If problems continue, contact the Point-of-Care Coordinator at extension 4431.


VI.              Results


§         Report and document patient results only if Performance Monitors perform as expected

§         Follow established nursing protocol on documentation of patient records

§         Hemoccult should give negative results with specimens from healthy subjects. 

§         Positive results should be reported to the physician immediately.

NOTE:  The test results of the Hemoccult Sensa cannot be considered conclusive evidence of the presence or absence of gastrointestinal bleeding or pathology.  The test is designed for preliminary screening as an aid to diagnosis, and are not intended to replace other diagnostic procedures.






VII.    Limitations


1.       The Hemoccult SENSA test is not recommended for use with gastric samples.

2.       Use Hemoccult SENSA Developer (blue label and cap) only with Hemoccult SENSA slides.  Do not use Gastroccult developing solution (orange cap).

3.       Substances that can cause false-positive results are:

Red meat, processed meats and liver;  raw vegetables and fruits which are high in peroxidase such as horseradish, turnips, melons and radishes;  the application of antiseptic preparations containing iodine to the anal area; ingestion of substances  which can irritate the gastrointestinal tract and cause bleeding, such as aspirin, corticosteroids, indomethacin, phenylbutazone, reserpine, anticoagulants, antimetabolites, cancer chemotherapeutic drugs, alcohol in excess, etc.

4.       Substances that can cause false negative results are:

Ascorbic Acid (Vitamin C) in excess of 250 mg per day; excessive amounts of Vitamin C enriched foods (citrus fruits and juices); Iron supplements that contain quantities of Vitamin C which exceeds 250 mg per day, if ingested.

5.       If developing slide immediately, failure to wait 3-5 minutes before developing will not allow the sample to absorb on the guaiac paper and can result in a false-negative result.

6.       Some specimens have a high bile content which causes the feces to appear green.  A distinct green color (no blue), appearing on or at the edge of the smear within 60 seconds after developing, should be interpreted as negative for occult blood.  A blue or blue-green color should be interpreted as positive.

7.       For accurate test results, patients must follow the Special Diagnostic Diet for at least 48 hours before and continuing through the sample collection period.


VIII.   Proficiency Testing


As an additional assurance of quality, two proficiency testing samples will be distributed three times annually.  These samples will be from the Occult Blood Survey (OCB) from CAP and will be distributed by the Pathology Department.  The survey will consist of two vials of a simulated fecal material. Only one select nursing unit will perform the survey per PT event.  Results of the PT will be reported on the Urinalysis Quality Management Report.


IX.      Competency Checks


Competency checks are performed at initial orientation, after 6 months of employement, and yearly thereafter by the POC Medical Technologist or a validated nurse.


X.       References:


Hemoccult SENSA, package insert.  SmithKline Diagnostics, Inc. San Jose, California.  November 1991.