Fecal Blood Tests Accurately Screen for Colon Cancer

A new generation of fecal blood tests can screen for colon cancer with unprecedented accuracy. However, the tests, although easily available, are greatly underused.

Many gastroenterologists believe that colonoscopy is the only test for colon cancer. But colonoscopy is expensive, uncomfortable, and carries the risk of damage such as internal bleeding. A simple fecal occult blood test, costing less than US$30 and performed in minutes, can single out the small percentage of the general population that would benefit from colonoscopy.

A study published in the September 25, 2007 issue of the Journal of the National Cancer Institute described two tests that use different methods to detect hidden blood. Each one has different pluses and minuses,” said study author Dr. James Allison, an investigator with the Kaiser Permanente division of research (Oakland, CA, USA). "We need to find out which is best--which we should be using in the United States and elsewhere.”

At least 10 fecal occult blood tests have been approved by the U.S. Food and Drug Administration (FDA; Bethesda, MD, USA). The most widely used is Hemoccult, which has been shown in controlled trials to reduce mortality from colorectal cancer.

One of the tests described in the report uses guaiac, the chemical in Hemoccult, as a detector. The other uses an immunochemical method. Screening of 5,841 people showed the immunochemical test to have a sensitivity of 81.8%, meaning that it detected that percentage of colorectal cancers and polyps. Moreover it had specificity--the ability to determine which people did not have the conditions--of 96.9%. The guaiac test was 64.3% sensitive and 90.1% specific.

Use of the tests not only saves lives but also reduces incidence of colorectal cancer by permitting removal of precancerous polyps, according to Jack Mandel, chairman of the department of epidemiology at Emory University (Atlanta, GA, USA) who wrote an accompanying editorial in the journal.

"We did the first large study at the University of Minnesota in 1993 to show that fecal blood testing reduces mortality, Professor Mandel said. There were 50,000 people in that trial. Two years later, we showed that testing reduced the incidence of colorectal cancer.”

Robert Smith, director of cancer screening for the American Cancer Society, said, "We recommend both guaiac-based tests and immunochemical tests. We recommend them for all adults age 50 and over. "The challenge has been to get folks to use them, in particular to get doctors to adopt them in the office.”


Related Links:
Kaiser Permanente
U.S. Food and Drug Administration
Emory University