Collins JF, Lieberman DA, Durbin TE, et al and the Veterans Affairs Cooperative Study #380 Group: Accuracy of screening for fecal occult blood on a single stool sample obtained by digital rectal examination: a comparison with recommended sampling practice. Ann Intern Med 2005;142(2):81-5.
Nadel MR, Shapiro JA, Klabunde CN et al: A national survey of primary care physicians' methods for screening for fecal occult blood. Ann Intern Med 2005;142(2):86-94.
Sox HC: Office-based testing for fecal occult blood: do only in case of emergency. Ann Intern Med 2005;142(2):146-8(editorial).
Rockey DC, Paulson E, Niedzwiecki D, et al: Analysis of air contrast barium enema, computed tomographic colonography, and colonoscopy: prospective comparison. Lancet 2005;365(9456):305-11.
The study by Collins and colleagues is the first to evaluate whether a single office-based fecal occult blood test (FOBT) has any screening value. In a population of asymptomatic male veterans 50 to 75 years of age, there was a 10.6% prevalence of advanced neoplasia (adenoma >10 mm, dysplastic or villous adenoma, or invasive cancer). Fecal occult blood tests done at home (2 samples from each of 3 stools) identified 24% of the neoplasia found on colonoscopy. A FOBT on a single sample of stool obtained by digital rectal examination only detected 4.9% of the patients with advanced colonic neoplasia.
Nadel and coauthors report that one-third of physicians use a single sample obtained in the office for FOBT as the sole method of colon cancer screening. In addition, after a positive FOBT result, many physicians report they perform either a follow-up FOBT or a sigmoidoscopy rather than going directly to a colonoscopy as recommended. To effectively screen for colorectal cancer, providers should recommend FOBT on six samples obtained at home or another type of screening test. Providers who rely on a single office FOBT sample will miss 95% of advanced neoplasia.
In the Rockey et al study, the authors recruited 614 patients who had positive FOBTs, iron deficiency anemia, or a family history of colon cancer. Patients underwent an air contrast barium enema (ACBE) followed a week later by computed tomographic colonography (CTC) and colonoscopy on the same day. The ability of these tests to detect colon polyps and cancers were reported. For lesions 10 mm or larger in size (n = 63), the sensitivity of ACBE was 48%, CTC 59%, and colonoscopy 98%. For lesions 6 to 9 mm in size, sensitivity was 35% for ACBE, 51% for CTC, and 99% for colonoscopy. Colonoscopy is more sensitive than either ACBE or CTC to detect colon polyps.