What an abnormal FIT result really means

In November 2013 British Columbia’s Colon Screening Program became fully available across the province. This important new program offers colorectal cancer screening to asymptomatic men and women between the ages of 50 and 74. 

Individuals at average risk are screened using the fecal immunochemical test (FIT), which has been available in British Columbia for the past 5 years and has been covered by MSP since April 2013. Because FIT is a relatively new test in this province, there has been some confusion about the test, particularly when there is an abnormal result.

FIT is a quantitative test with a threshold of 50 nanograms per millilitre of hemoglobin. While FIT is a good screening test, it is important that patients understand that FIT is not a diagnostic test, regardless of the level of blood present in the sample submitted.

FIT can only tell us that there may be bleeding from somewhere in the lower digestive tract. It cannot tell us from which part or why. Blood can be present in the stool for many reasons, including hemorrhoids, ulcers, anal fissures, diverticular disease, or inflammation. And, like any test, FIT may give an abnormal result even though there is nothing wrong.

On average, 15% of individuals screened with FIT will have an abnormal FIT result and will require additional testing. This does not mean that a cancer was found—over 96% of those with an abnormal FIT will not have cancer. Some of these patients may have adenomas (precancerous polyps). Most adenomas will never turn into cancer, and for those that do, it will take many years for this transition, which is why patients should be screened regularly. 

Colonoscopy is necessary after an abnormal FIT to ensure that no cancer is present. Removal of adenomas at colonoscopy has been shown to decrease the mortality and incidence of colorectal cancer. Colonoscopy is a safe and accurate test, and quality assurance programs are being implemented throughout the province to ensure the safety and efficacy of colonoscopy are maximized.

For more information on FIT or the Colon Screening Program, visit www.screeningbc.ca. 
—Jennifer J. Telford, MD
Medical Director, BC Cancer Agency Colon Screening Program