Use of Colorectal Cancer Screening by Doctors in Practice

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The summary below is from the full report titled "A National Survey of Primary Care Physicians' Methods for Screening for Fecal Occult Blood." It is in the 18 January 2005 issue of Annals of Internal Medicine (volume 142, pages 86-94). The authors are M.R. Nadel, J.A. Shapiro, C.N. Klabunde, L.C. Seeff, R. Uhler, R.A. Smith, and D.F. Ransohoff.

What is the problem and what is known about it so far?

Colorectal cancer is a leading type of cancer and a leading cause of cancer death in the United States. Screening for colorectal cancer can lower the risk for dying of colorectal cancer by finding growths (polyps) before they become cancer or by finding cancer at an early, curable stage. Available screening tests include the fecal occult blood test (FOBT) and colonoscopy. Fecal occult blood testing usually uses a chemical reaction on a paper card to find traces of blood that can leak from polyps and cancer into the stool. Colonoscopy involves looking for polyps and cancer in the colon through a flexible tube. Fecal occult blood testing is simpler and less expensive than colonoscopy, and research shows it can reduce the risk for dying of colorectal cancer. However, for the test to be effective, it must be performed by collecting several stool samples at home, and a positive result must be followed by colonoscopy to look for the source of the blood. It is not known if doctors follow these standards in practice.

Why did the researchers do this particular study?

To see if doctors follow recommended standards for performing FOBT when they screen patients for colorectal cancer.

Who was studied?

1147 primary care doctors and 11,365 people 50 years of age and older who were eligible for colorectal cancer screening. The latter group were part of a national government survey performed in 2000 to better understand health in the U.S. population.

How was the study done?

The researchers sent a survey to the primary care doctors asking them if and how they used FOBT and what additional testing they recommend for patients with an abnormal test result. They asked adults eligible for colorectal cancer screening if they had ever had FOBT and what additional tests they had if the results were abnormal.

What did the researchers find?

More than 90% of the doctors used FOBT at least once per month. One third of these used the test only in their office rather than giving it to patients for use at home. Close to one third repeated the test if the results were abnormal rather than immediately referring the patient for colonoscopy. About 1 in 4 of the surveyed patients reported having FOBT; of these, about one third reported having the test in the doctor's office only. Ten percent reported having an abnormal test result; less than half of them were referred for colonoscopy.

What are the limitations of the study?

The researchers relied on what doctors and survey participants said rather than measuring the number of screening tests and test results. Because doctors tend to overrate how well they screen patients for cancer and because patients often forget or misunderstand what tests they have had, the study's estimates may be inaccurate.

What are the implications of the study?

Doctors frequently use FOBT to screen patients for colorectal cancer in ways that differ from standard recommendations. As a result, the benefits of FOBT for reducing the risk for cancer and cancer death might be less than expected. Patients who choose FOBT for colorectal cancer screening should ask for the home test instead of having it in the doctor's office, and they should have colonoscopy to follow up any positive results.