High Percentage of Docs Use FOBT Inappropriately, Study Finds

In-office Test Unreliable for Colorectal Cancer Screening

May 25, 2010 06:50 pm David Mitchell

The majority of primary care physicians who order or perform fecal occult blood tests, or FOBTs, to screen for colorectal cancer fail to follow recommended guidelines for such screenings. That's according to a study(www.springerlink.com) in the Journal of General Internal Medicine.

The study, which was sponsored by the National Cancer Institute, the CDC and the Agency for Healthcare Research and Quality, used data from 2006-07. Researchers surveyed more than 1,100 primary care physicians. Of those participants, 25 percent reported using in-office FOBTs exclusively to screen for colorectal cancer, and more than 50 percent reported using both in-office and home tests.

Only 22 percent of respondents used home-based FOBT exclusively for the majority of their patients, and less than half of those who used home tests had reminder systems to ensure that patients completed and returned the tests.

That's despite the fact that for nearly a decade, the use of serial home-based FOBTs rather than a single in-office FOBT has been recommended by the American Cancer Society, or ACS, for patients who, together with their physicians, decide on annual FOBT as a colorectal cancer screening strategy.

Summary of USPSTF, AAFP Colorectal Cancer Screening Recommendations

The U.S. Preventive Services Task Force, or USPSTF, and the Academy recommend three preferred strategies for routine colorectal cancer screening for average-risk men and women between the ages of 50 and 75:

  • annual high-sensitivity fecal occult blood test, or FOBT, or
  • flexible sigmoidoscopy every five years combined with FOBT every three years, or
  • colonoscopy every 10 years.

Although the recommendation itself does not specifically address single in-office screening with FOBT versus serial at-home FOBTs, its supporting materials referred to the fact that "data suggested better detection of colorectal cancer and large adenomas with 2 to 3 days of sample collection for FOBTs than with 1 day of sample collection."

According to Michael Potter, M.D., a professor in the department of family and community medicine at the University of California, San Francisco, and a member of the National Colorectal Cancer Roundtable, home stool testing programs, which emphasize annual test completion with appropriate follow-up, remain an important option for screening, especially in settings where resources are limited or when average-risk patients prefer tests that are less invasive than colonoscopy.

At-home FOBT Versus In-office FOBT

According to a 2003 update of the ACS' guidelines for the early detection of cancer, "FOBT as it is sometimes done in physicians' offices, with the single stool sample collected on the fingertip during a digital rectal examination, is not an adequate substitute for the recommended at-home procedure of collecting two samples from three consecutive specimens."

Even two years earlier, the ACS' guidance on colorectal cancer screening noted that if patients and their physicians chose to screen using annual FOBT, "the recommended take-home multiple sample method should be used."

According to Michael Potter, M.D., a professor in the department of family and community medicine at the University of California, San Francisco, there may be sound clinical reasons to complete an in-office FOBT -- such as to evaluate for subacute upper gastrointestinal bleeding -- but it should never be used as a method to screen for colorectal cancer.

"Single-sample, in-office guaiac FOBT has an extremely low sensitivity, so a negative test can only provide false reassurance to patients and their physicians," Potter said in an interview with AAFP News Now.

"We have had recommendations against in-office FOBT for screening for years now, so it is hard to understand why physicians would use an in-office guaiac test for screening even some of the time," he added.

2008 Joint Screening and Surveillance Guidelines

In 2008, the ACS, the American College of Radiology; and the U.S. Multi-Society Task Force on Colorectal Cancer issued joint guidelines for screening and surveillance for the early detection of colorectal cancer and adenomatous polyps.

Those guidelines specify that if patients and their physicians select guaiac-based FOBTs, or gFOBTs, for screening, the test must be performed with three stool samples obtained at home. The authors also note that the accuracy of in-office gFOBT screening -- a single-panel test performed using a sample obtained during a digital rectal exam -- "is so low that it cannot, under any circumstances or rationale of convenience, be endorsed as a method" of screening.

"We used to say that the best colon cancer screening test is the one that gets done," said Potter, who has served on the Quality Assurance Subcommittee of the National Colorectal Cancer Roundtable and is a recipient of the ACS' Cancer Control Career Development Award for Primary Care Physicians. "Perhaps not enough emphasis has been placed on which tests should not be done. In-office FOBT should be at the top of that list."

It remains unclear what percentage of physicians have changed their screening methods since the release of the 2008 guidelines.

Authors of the recent Journal of General Internal Medicine study said their survey results showed no evidence of a shift away from the use of in-office tests, despite published evidence of low accuracy of in-office FOBT coupled with a change in CPT codes that was intended to reinforce appropriate use of FOBT.

Higher Colorectal Cancer Mortality Among Blacks Tied to Follow-up, Study Suggests

Previous research had indicated that mortality from colorectal cancer among blacks is more common than among whites in the United States, but a new study(jnci.oxfordjournals.org) in the Journal of the National Cancer Institute suggests the disparity may have more to do with health care utilization than biology.

Researchers used data from the ongoing Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial. More than 60,000 black and non-Hispanic white study participants underwent flexible sigmoidoscopic screening for colorectal cancer, and suspicious lesions were found in similar percentages of blacks (25.5 percent) and whites (23.9 percent).

However, the researchers found, 72.4 percent of white participants followed up on their physician's recommendation for diagnostic colonoscopy, compared with 62.6 percent of blacks.

Specifically, a new CPT code was introduced in 2006 to distinguish home FOBT from the in-office test, and Medicare only reimburses for colorectal cancer screening with FOBT if the new code is used.

The 2006-07 survey followed a 1999-2000 survey(www.annals.org) that also found that many primary care physicians used inadequate methods to implement screening and follow-up.

Use of High-sensitivity Tests and Appropriate Follow-up

Most physicians reported in the 2006-07 survey that they used standard guaiac tests, with only 22 percent and 9 percent of respondents, respectively, reporting the use of higher-sensitivity guaiac tests and immunochemical tests.

"There is now a gradual migration away from the use of low-sensitivity guaiac tests toward higher-sensitivity tests, such as home fecal immunochemical tests, as the preferred method of home stool testing for colorectal cancer," Potter said. "The introduction of these new and improved stool-based technologies should be seized upon as an opportunity to educate clinicians and improve the quality of colorectal cancer screening in primary care."

In addition, the joint guidelines recommend colonoscopy as the follow-up procedure to a positive FOBT. But, nearly 18 percent of physicians surveyed in 2006-07 recommended repeating FOBT instead, although that figure was an improvement on the 30 percent of physicians whose follow-up practices were inconsistent with recommended standards in the 1999-2000 survey.

"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," the study says.

Colorectal cancer is the third most common cancer diagnosed in the United States and the second leading cause of death from cancer.