Colorectal Cancer Screening

Optical or visualization screening tests

Colonoscopy - A procedure where a doctor looks into the rectum and the entire colon using a flexible narrow tube to identify colorectal cancer or precancerous polyps. Used not only as a screening test, colonoscopies are also used as a diagnostic procedure to follow up after positive results from a fecal occult blood test (FOBT) or fecal immunochemical test (FIT), fecal DNA test, sigmoidoscopy, or CT colonography. The USPSTF suggests a screening colonoscopy once every 10 years.

Computed tomography (CT) colonography (otherwise known as a virtual colonoscopy) - Produces a three-dimensional image of the colon which your doctor examines for colorectal cancer and precancerous polyps. The USPSTF suggests CT colonography once every 5 years.

Sigmoidoscopy - A procedure where a doctor looks into the rectum and part of the colon using a flexible narrow tube to identify colorectal cancer or precancerous polyps. The USPSTF suggests sigmoidoscopy once every 5 years, or once every 10 years when conducted along with FIT every year.

Stool-based screening tests

Fecal occult blood test (FOBT) and fecal immunochemical test (FIT) - These tests identify hidden blood in the stool, which can be a sign of cancer. The USPSTF suggests FOBT or FIT annually, using a home-based kit.

Fecal DNA test – In addition to checking for hidden blood in the stool like a FIT, this test also looks for abnormal genetic material that may be a sign of colorectal cancer. The USPSTF suggests fecal DNA testing at least every 3 years.

Measurement challenges

We track colorectal cancer screening rates in the U.S. using a large, national, in-person survey in which people are asked about their health behaviors and the medical care they receive (see Data Source, below). There are important limitations to this method that impact what information we can accurately collect and how confident we can be in the findings. Studies have found that certain types of healthcare survey questions can be difficult for people to clearly understand and answer, and it is easy for some questions to be misinterpreted.

In the case of colorectal screening, it may be challenging to determine by self-report alone if a colonoscopy was received for screening purposes, i.e., to look for asymptomatic, previously undetected cancer, or for diagnostic purposes, i.e., as a follow up on symptoms or suspicious findings from a prior test. It can also be difficult to determine by self-report alone which type of colorectal cancer screening test a person received, as several testing options appear similar to the person experiencing them. People may also not always accurately recall the specific time they received a particular test. Additionally, cancer screening is looking for cancer before a person has symptoms, when they are not known to have had that specific cancer type before. Looking for new or recurrent asymptomatic cancer in a person previously diagnosed and treated for that cancer type represents a different type of testing known as surveillance testing.

Options for colorectal cancer screening have increased over time, which results in a greater likelihood for missing or incomplete self-reported information about the screening tests people received. Different approaches by researchers for handling this missing information can result in somewhat varied estimates presented for up-to-date colorectal cancer screening status, depending on publication.

Our measure captures general receipt of a colorectal cancer screening test (yes/no) more accurately than its underlying purpose or the specific screening test received, and the population may include those with a prior diagnosis of colorectal cancer. This serves as a reasonable approximation of the true U.S. colorectal cancer screening rate, but the measure is not perfectly comparing the actual frequency of people’s use of colorectal cancer screening to national recommendations.

Even though the National Health Interview Survey colorectal cancer screening measures have limitations, it is the best nationally representative data we have available to assess colorectal cancer screening rates. It is frequently used by governmental and other organizations to track screening use over time in the US.