Stool For Occult Blood

The method of collection and testing depends on the test procedure used and can vary from laboratory to laboratory. For the guaiac-based test, the laboratory will provide three test cards. Separate stool samples are collected on three consecutive days and for each test, a stool sample should be collected into a clean container and should not be contaminated with urine or water. A test card is labeled with the person's name and the date. A thin smear of stool is put onto a designated area on the card and allowed to dry. Once it is dry, it is stable for several weeks at room temperature. When all the consecutive samples have been collected and dried, the test cards are returned to the health practitioner or laboratory, usually by mailing them. With the OTC flushable reagent pad/tissue method, a test pad/tissue is placed in the toilet after a bowel movement. The pad contains a chemical that produces a color change when blood is present. The person doing the test watches for the characteristic color change and records the findings on a report form. Like the gFOBT, this test is usually done on three consecutive days and then the completed form is returned to the health practitioner. The use of toilet bowl cleansers or the presence of blood-derived from urine or a woman's menstrual period may alter results. With the fecal immunochemical tests (FIT), a common approach is to use a special long-handled brush or any other device in order to collect a sample from the surface of a stool sample. The brush or device is then used to transfer the sample to a special collection card. After the card is allowed to dry, it is returned to the laboratory for further analyses.

Inform the doctor about the medications you may be taking. No other specific preparations are usually required before this test.

Other available tests to screen carcinoma colon include Sigmoidoscopy which is an endoscopic examination of the rectum and lower colon. If polyps are found, they may be removed during the procedure and examined by a pathologist to see if cancer is present. Screening with sigmoidoscopy should be done once every 5 years; Colonoscopy which is a more thorough examination of the rectum and entire colon using a flexible endoscope. If polyps are found, they may be removed during the procedure and examined by a pathologist to see if cancer is present. This procedure is recommended for screening every 10 years; CT colonoscopy (virtual colonoscopy) which uses computed tomography to visualise the entire colon. The recommended screening interval is 5 years and Double-contrast barium enema which is a series of X-rays of the colon and rectum is taken. It is recommended every 5 years.

Bleeding, especially from polyps and tumors, is periodical. Therefore, blood is not uniformly distributed in all stool samples. This means an exact interpretation of results from a single test cannot be made. Hence, taking three different samples on three different days can increase the chances of detecting occult bleeding.