FOBT screening saves lives, but only when it is done right.
Three out of four primary care doctors did a fecal occult blood test once during an office visit, a method that is ineffective in finding cancer or preventing death from colorectal cancer. One out of four used the in-office test exclusively.
Less than half of doctors had a system in place to be sure that home tests were completed and returned.
What Primary Care Doctors are Doing
The 2006–2007 National Survey of Primary Care Physicians Recommendations and Practices for Cancer Screening conducted by the National Cancer Institute in collaboration with CDC and the Agency for Healthcare Research and Quality surveyed a sample of primary care doctors about their recommendations for colorectal cancer screening. Family physicians, general practitioners,obstetrician-gynecologists, and internists were included.
Over ninety percent of surveyed doctors said that they used an FOBT for colorectal screening at least once a month. Of those 24.8 percent performed the test only in their offices, 52.9 percent used both office and home tests. Three out of five doctors used a test that is no longer recommended because of its low sensitivity.
A single in-office test during a rectal exam will miss 95 percent of cancers and advanced polyps.
In other practices that reduced the value of fecal occult blood tests:
- Almost 1 in 5 doctors (17.8 percent) repeated a positive FOBT rather than refer a patient for colonoscopy immediately.
- Of those doctors who repeated FOBT, nearly a third (28.8 percent) stopped follow-up evaluation if the second FOBT was negative.
- Most doctors (61.1 percent) were using the least sensitive test, a standard guaiac test, which is no longer recommended. Only 22 percent used the higher sensitivity guaiac test and 8.9 percent used a fecal immunohistochemical test which is more sensitive and doesn’t require patients to follow a special diet or refrain from certain medications before the test. 14.7 percent didn’t know what test they used.
- Only 44.3 percent had a system in place — chart reminders, telephone calls, or mailings — to follow up on FOBTs that weren’t returned.
- 62.2 percent of doctors had no system in place to be sure that patients referred for follow-up evaluation of a positive test actually got that testing.
Writing in the Journal of General Internal Medicine, CDC scientist Marion Nadel PhD and her team said,
While FOBT done appropriately is an important screening option, in-office FOBT may be worse than no screening at all because it misses 95% of cases of advanced neoplasia, giving many patients a false sense of reassurance.
The researchers concluded,
Although FOBT is an important option for colorectal cancer screening, our study suggests that its potential to save lives is not currently being realized because many physicians are continuing to use inappropriate implementation methods. Intensified efforts to inform physicians of recommended technique and promote the use of systems for tracking test completion and follow-up are needed.
What the Recommendations Are
Both the American Cancer Society and the US Preventive Services Task Force have fecal occult blood testing as a colorectal cancer screening option.
Early Detection of Colorectal Cancer and Adenomatous Polyps, 2008: A Joint Guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology recommend the following as an option for the early detection of colorectal cancer in adults over 50 without symptoms:
Annual fecal immunochemical test with high test sensitivity for cancer.
They further point out:
Because small adenomatous polyps do not tend to bleed and bleeding from cancers or large polyps may be intermittent or simply not always detectable in a single sample of stool, the proper use of stool blood tests requires annual testing that consists of collecting specimens (2 or 3, depending on the product) from consecutive bowel movements.
When a test is positive, follow-up with colonoscopy that examines the entire length of the colon is required:
When performed for CRC screening, a positive gFOBT or FIT requires a diagnostic workup with colonoscopy to examine the entire colon in order to rule out the presence of cancer or advanced neoplasia.
The guidelines specifically specify high-sensitivity guaiac FOBT such as Hemoccult SENSA or fecal immunohistochemical tests (FIT) instead of the older guaiac FOBT. The test should be done at home on three consecutive bowel movements. There are some FIT tests that require fewer samples, and most FITs don’t have diet and medicine limits prior to testing, but they still need to be done more than once and at home.
The US Preventive Services Task Force also recommends annual high-sensitivity fecal occult blood testing as one option for colorectal cancer screening in average risk adults from 50 to 75. USPSTF doesn’t directly address the issue of how to do that screening, but does embrace the idea of choice.
Because several screening strategies have similar efficacy, efforts to reduce colon cancer deaths should focus on implementation of strategies that maximize the number of individuals who get screening of some type. The different options for colorectal cancer screening tests are variably acceptable to patients; eliciting patient preferences is one step in improving adherence. Ideally, shared decision making between clinicians and patients would incorporate information on local test availability and quality as well as patient preferences.
What This Means for Patients
Fecal occult blood testing (FOBT) is a recommended colorectal screening option for people of average risk.
It is especially useful for screening where there is limited access to sigmoidoscopy or colonoscopy. Some patients may prefer it over options that are more invasive or require bowel preparation. It should be choice for you to consider.
However, it is critical that it be done right.
- Don’t accept a single test done in your doctor’s office during a rectal exam. It will find so few cancers that it is useless.
- Ask for a high sensitivity guaiac FOBT or a fecal immunohistochemical test (FIT). Medicare and most insurances will cover either one.
- Be sure to follow instructions carefully in the days before starting the test. Complete all samples, and mail the test back.
- If your doctor doesn’t follow-up, call and find out if the results were normal.
- If the test is positive, insist on a colonoscopy. Don’t accept a second test or a less complete examination of your entire colon.
Then repeat the test in a year.