Decision box

The fecal occult blood test estimates the risk of having colorectal cancer. If the test is positive, the physician usually offers a diagnostoc test, such as colonoscopy, to verify that the individual has colorectal cancer.

Stool stamples are tested for presence of occult blood every one to two years.

Individuals at average risk for colorectal cancer, that is: 

• Individuals between 50 -75 years of age. 
• Individuals younger than 50 with first degree relatives who developed  cancer before 50 years old, or with multiple affected first-degree relatives. 

This test does not apply to individuals at greater than average risk for colorectal cancer who should follow guidelines specific to their personal and family histories. Risk factors that put an individual at greater than average risk for colorectal cancer are : inflammatory bowel disease and certain inherited syndromes (Lynch syndrome/hereditary nonpolyposis colorectal cancer (HNPCC), Familial polyposis syndromes)

There are pros and cons to this screening test: 

• PROS: For each 1000 individuals screened every one or two tears during 13   years, 1 death from colorectal cancer is prevented, but no death from all cause is prevented.
• CONS: Screening can be inaccurate and cause harms. For each 1000 individuals screened, 3 test negative with the FOBT but they will actually have a cancer, and 20 test positive but do not have colorectal cancer. Those who test positive will undergo colonoscopy to verify if they have colorectal cancer, and this can have serious but uncommon side effects.