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Adapted from the NCI Cancer Bulletin, vol. 4/no. 26, Sept. 25, 2007 (see the current issue ²).

In a large prospective study performed by investigators from three Northern California Kaiser Permanente medical centers, a type of fecal occult blood test (FOBT) called a fecal immunochemical test (FIT) showed high sensitivity and specificity for detecting left-sided colorectal cancer. The results were published online on September 25, 2007, by the Journal of the National Cancer Institute (see the journal abstract ³).

The investigators enrolled 7,394 eligible Kaiser Foundation Health Plan members aged 50 or older without a personal or family history of colon cancer into the study. All participants collected stool samples for use on three test cards, and the samples on each test card were used for three tests: a sensitive unrehydrated guaiac test (GT, a more sensitive version of the current standard FOBT), the FIT, and a combination of those two tests. Out of all participants, 5,841 prepared cards correctly and had at least one usable test result. Of these, 11 percent had at least one positive result.

Investigators recommended that all participants testing positive on the FIT or combination tests undergo colonoscopy, and all participants testing negative undergo sigmoidoscopy. Because most participants tested negative and underwent sigmoidoscopy, which can only visualize the left colon, only detection of left-sided colorectal cancer could be compared between tests. All participants were followed for two years, until diagnosis of a colorectal neoplasm, or until death, whichever came first.

The FIT had an 81.8 percent sensitivity for detecting colorectal carcinoma, and a 29.5 percent sensitivity for detecting advanced colorectal adenomas (noncancerous tumors). Specificity was 96.9 percent for carcinomas and 97.3 percent for adenomas, which increased to 98.1 percent and 98.4 percent in the combination test.

Although the investigators did not directly compare the FIT test with the current standard FOBT test, other recent comparisons have shown its superiority, they explain. "The FIT has high sensitivity and specificity for detecting left-sided colorectal cancer," they conclude, "and it may be a useful replacement for the [current standard test]."

Glossary Terms

A tumor that is not cancer. It starts in gland-like cells of the epithelial tissue (thin layer of tissue that covers organs, glands, and other structures within the body).

Cancer that begins in the skin or in tissues that line or cover internal organs.

Examination of the inside of the colon using a colonoscope, inserted into the rectum. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue to be checked under a microscope for signs of disease.

A test to check for blood in the stool. Small samples of stool are placed on special cards and sent to a doctor or laboratory for testing. Blood in the stool may be a sign of colorectal cancer. Also called fecal occult blood test.

An abnormal mass of tissue that results when cells divide more than they should or do not die when they should. Neoplasms may be benign (not cancer), or malignant (cancer). Also called tumor.

In medicine, a study or clinical trial in which participants are identified and then followed forward in time.

When referring to a medical test, sensitivity refers to the percentage of people who test positive for a specific disease among a group of people who have the disease. No test has 100% sensitivity because some people who have the disease will test negative for it (false negatives).

Examination of the lower colon using a sigmoidoscope, inserted into the rectum. A sigmoidoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue to be checked under a microscope for signs of disease. Also called proctosigmoidoscopy.

When referring to a medical test, specificity refers to the percentage of people who test negative for a specific disease among a group of people who do not have the disease. No test is 100% specific because some people who do not have the disease will test positive for it (false positive).

The material in a bowel movement. Stool is made up of undigested food, bacteria, mucus, and cells from the lining of the intestines. Also called feces.