A Comparison of Fecal Occult-Blood Tests for Colorectal-Cancer Screening

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Abstract

Hemoccult II, a widely used guaiac test for fecal occult blood, has a low sensitivity for detecting colorectal neoplasms in asymptomatic patients at average risk. In such patients, the performance characteristics of screening tests developed to improve on Hemoccult II are not known. A set of three fecal occult-blood tests--Hemoccult II; Hemoccult II Sensa, a more sensitive guaiac test; and HemeSelect, an immunochemical test for human hemoglobin--was mailed to all patients 50 years of age or older who were scheduled for personal health appraisals at the Kaiser Permanente Medical Center in Oakland, California. The performance of each test and of a combination test (HemeSelect to confirm positive Hemoccult II Sensa results) was evaluated by identifying screened patients who had colorectal neoplasma (carcinoma or a polyp > or = 1 cm in diameter) in the two years after screening. Of the 10,702 eligible patients, 8104 (75.7 percent) had at least one interpretable sample and were screened on the basis of at least one test; 96 percent of these patients had complete two-year follow-up. The sensitivity of the tests for detecting carcinoma was lowest with Hemoccult II (37.1 percent; 95 percent confidence interval, 19.7 to 54.6 percent), intermediate with the combination test (65.6 percent; 95 percent confidence interval, 47.6 to 83.6 percent) and with HemeSelect (68.8 percent; 95 percent confidence interval, 51.1 to 86.4 percent), and highest with Hemoccult II Sensa (79.4 percent; 95 percent confidence interval, 64.3 to 94.5 percent). The specificity for detecting carcinoma was 86.7 percent with Hemoccult II Sensa, 94.4 percent with HemeSelect, 97.3 percent with the combination test, and 97.7 percent with Hemoccult II. HemeSelect and the combination test detected more colorectal carcinomas and polyps than Hemoccult II, with only slight increases in the number of colonoscopies needed. HemeSelect and a combination test in which HemeSelect is used to confirm positive Hemoccult II Sensa results improve on Hemoccult II in screening patients for colorectal carcinoma.

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Most cited references 14

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Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study.

Jack Mandel, John Bond, Timothy R Church … (1993)

Although tests for occult blood in the feces are widely used to screen for colorectal cancers, there is no conclusive evidence that they reduce mortality from this cause. We evaluated a fecal occult-blood test in a randomized trial and documented its effectiveness. We randomly assigned 46,551 participants 50 to 80 years of age to screening for colorectal cancer once a year, to screening every two years, or to a control group. Participants who were screened submitted six guaiac-impregnated paper slides with two smears from each of three consecutive stools. About 83 percent of the slides were rehydrated. Participants who tested positive underwent a diagnostic evaluation that included colonoscopy. Vital status was ascertained for all study participants during 13 years of follow-up. A committee determined causes of death. A single pathologist determined the stage of each tissue specimen. Differences in mortality from colorectal cancer, the primary study end point, were monitored with the sequential log-rank statistic. The 13-year cumulative mortality per 1000 from colorectal cancer was 5.88 in the annually screened group (95 percent confidence interval, 4.61 to 7.15), 8.33 in the biennially screened group (95 percent confidence interval, 6.82 to 9.84), and 8.83 in the control group (95 percent confidence interval, 7.26 to 10.40). The rate in the annually screened group, but not in the biennially screened group, was significantly lower than that in the control group. Reduced mortality in the annually screened group was accompanied by improved survival in those with colorectal cancer and a shift to detection at an earlier stage of cancer. Annual fecal occult-blood testing with rehydration of the samples decreased the 13-year cumulative mortality from colorectal cancer by 33 percent.

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Screening for colorectal cancer with fecal occult blood testing and sigmoidoscopy.

S J Winawer, B J Flehinger, D Schottenfeld … (1993)

The high incidence of and mortality from colorectal cancer (160,000 new cases and 60,000 deaths in the United States each year) are compelling public health concerns. Following the evolution of effective surgery for this disease since the 1960s, the focus has been on improving methods of detection and integrating them into effective screening programs. This was the first study to evaluate the effectiveness, in a setting of comprehensive medical examinations, of using the fecal occult blood test in conjunction with sigmoidoscopy, rather than sigmoidoscopy alone, to screen for colorectal cancer. Our end points were extent of compliance with fecal occult blood test and sigmoidoscopy, numbers of cancers detected, and mortality rate. From 1975 through 1979, a total of 21,756 patients (aged 40 and older) who presented at the Preventive Medicine Institute-Strang Clinic for routine medical examinations were enrolled by calendar period into study and control groups. Study patients were offered annually both rigid sigmoidoscopy examinations and fecal occult blood tests requiring two stool specimens per day for 3 days, while control patients were offered only annual sigmoidoscopy. The majority of fecal occult blood test cards were not rehydrated before assay. Patients with positive tests were referred for double-contrast barium enema and colonoscopy. Two distinct trials were carried out. Trial I was primarily a demonstration of feasibility of using the fecal occult blood test as a supplemental screening method. Of the 9277 participants, 7168 (77%) were assigned to the study group and offered the fecal occult blood test. In trial II, approximately half of the 12,479 patients were assigned to each group. Patients in both trials had follow-up through 1984. Compliance with the fecal occult blood test was initially high in both trials, but diminished such that only 56% of study patients in trial I and 20% of those in trial II returned for second tests. On the initial (prevalence) screen, a substantial number of early-stage cancers were detected by the fecal occult blood test, primarily in trial II. In trial II, survival probability was significantly greater (P < .001) in the study group than in the controls (70% versus 48%), and colorectal cancer mortality was lower (0.36 versus 0.63) with borderline significance (P = .053, one-sided). The screening of average-risk individuals (aged 50 and older) for colorectal cancer through use of the fecal occult blood test in conjunction with sigmoidoscopy can increase the likelihood of early detection of this disease. This practice, coupled with prompt diagnostic work-up following positive tests, will result in treatment of earlier stage cancers and increased survival after treatment.

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Occult blood screening for colorectal carcinoma: a critical review.

Jerome Simon (1985)

The author reviews the literature on occult blood surveillance for colorectal carcinoma. The guaiac-based Hemoccult (SmithKline Diagnostics, Sunnyvale, Calif.) test is the most reliable and widely used. However, testing is complicated by several technical issues that can affect clinical results, and even successful screening programs will miss a high proportion of tumors. Public compliance is often poor, and a number of indirect and "hidden" costs make surveillance programs much more expensive than is usually claimed. Almost all published screening trials are uncontrolled. They generally detect about 3-20 colorectal malignancies for every 10,000 people enrolled, but only about 5%-10% of occult blood reactions are due to cancer. Though screen-detected tumors tend to be at a relatively early stage, this does not imply any benefit of surveillance because of lead time and length biases inherent in the screening process. Only controlled trials can answer the central question of whether screening decreases mortality from bowel cancer. Two such trials are underway, but mortality data are not yet available from either.