Occult Blood Test

Occult blood test screens for colorectal cancer

An occult or "hidden" blood test is a screening test for colorectal cancer, the second leading cause of cancer death in the U.S. The word colorectal refers to the colon or large intestine, and the rectum, the end of the digestive system. The specimen is a small sample of feces that is smeared onto a card and can be taken in the doctor's office or at home. The specimen on the card is then chemically tested for the presence of blood. Certain foods and medications, such as aspirin and ibuprofen, should be avoided before taking an occult blood test.

A positive fecal occult blood result may indicate bleeding in the colon or rectum and shows increased risk of colorectal cancer. Other tests also used for colorectal cancer screening are barium enema, colonoscopy, sigmoidoscopy and digital rectal examination.

The incidence of colorectal cancer in men and women is about equal. People at higher risk of developing the disease include:

  • People over the age of 50
  • People who have a family history of colorectal cancer
  • People who have previously had colorectal cancer

Most doctors recommend fecal occult blood screening every year for everyone over 50. Early detection of colorectal cancer greatly improves the odds of successful treatment.