U.S. flag

An official website of the United States government

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

US Public Health Service. Office of Disease Prevention and Health Promotion. Clinician's Handbook of Preventive Services. 2nd edition. Washington (DC): Department of Health and Human Services (US); 1999.

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

Cover of Clinician's Handbook of Preventive Services

Clinician's Handbook of Preventive Services. 2nd edition.

Show details

34Fecal Occult Blood

In 1997, approximately 131,200 new cases of colorectal cancer will occur, resulting in 54,900 deaths. Principal risk factors for colorectal cancer include a history of one of the familial polyposis syndromes, familial cancer syndromes, colorectal cancer in first-degree relatives, or a personal history of ulcerative colitis, adenomatous polyps, or endometrial, ovarian, or breast cancer. Colorectal cancer detected at an early stage can be successfully treated with surgery.

Malignancies and, to a lesser extent, polyps, bleed intermittently. Fecal occult blood tests (FOBT) can detect this bleeding by identifying occult blood or breakdown products of blood in fecal material. The reported sensitivity of FOBT for detecting colorectal cancer in asymptomatic individuals ranges from 26% to 92% but with most data suggesting a sensitivity of less than 40%. The specificity ranges form 90% to 99%. Measures of sensitivity and specificity are usually based on two samples from three consecutive and easily passed stools.

Until recently, no studies had shown that fecal occult blood testing resulted in decreased mortality. In 1993, however, Mandel et al found that yearly fecal occult blood testing using rehydrated stool specimens decreased mortality from colorectal cancer by about one third. In that study, guaiac-impregnated paper slides were used to test for fecal blood.

Rehydration of dried samples before testing can increase sensitivity but also produces more false-positive results. The predictive value of a positive fecal occult blood test for colorectal cancer in general populations is only 5% to 10%. Thus, up to 75% of cancers will be missed, and for every case of colorectal cancer that is detected by fecal occult blood testing, up to 20 patients will undergo workups that will be negative.

See chapters 30 and 41 for information about other methods of screening for colorectal cancer.

Recommendations of Major Authorities

  • American Academy of Family Physicians --
  • Adults aged 40 years and older with a family history of early colorectal cancer and all adults aged 50 years and older should be screened for colorectal cancer with fecal occult blood testing (annually), sigmoidoscopy, colonoscopy, or barium enema.
  • American Cancer Society --
  • Annual fecal occult blood testing is recommended in combination with flexible sigmoidoscopy every 5 years in normal risk individuals beginning at 50 years of age. The American Cancer Society further recommends that digital rectal examination be performed along with sigmoidoscopy. (See chapter 41 for details.)
  • American College of Obstetrics and Gynecology --
  • Fecal occult blood testing should be done for all women 50 years of age and older as part of their periodic health examination.
  • American College of Physicians --
  • Persons who decline screening colonoscopies and barium enemas, and especially people who decline screening flexible sigmoidoscopies, should be offered annual fecal occult blood testing from 50 to 70 or 80 years of age. No recommendation is made about the optimal frequency for screening with FOBT. In general, persons who have positive results on a fecal occult blood test should have a full colonic examination. More research is needed to understand and improve the sensitivity and specificity of the fecal occult blood test.
  • Canadian Task Force on the Periodic Health Examination(CTFPHE) --
  • There is insufficient evidence to recommend including or excluding fecal occult blood testing in the periodic health examination of individuals over 40 years of age. There is also insufficient evidence to provide fecal occult blood testing to adults at risk because of family history. Patients with true cancer family syndrome should be screened with colonoscopy, not fecal occult blood testing.
  • US Preventive Services Task Force --
  • Screening for colorectal cancer is recommended for all persons 50 years of age or older. This can be accomplished with annual fecal occult blood testing or sigmoidoscopy (frequency unspecified). There is insufficient evidence to determine which method is preferable or whether combining both methods produces results superior to either method alone.

Basics of Fecal Occult Blood Screening

1.

Three types of tests are available for detecting fecal occult blood: guaiac-impregnated cards and other carriers that detect the peroxidase-like activity of hemoglobin (Hemoccult®); quantitative tests based on the conversion of heme to fluorescent porphyrins (HemoQuant®); and immunoassay tests for human hemoglobin. Currently only the first two types are routinely used in practice. Guaiac-based tests have the disadvantage of giving false-negative and false-positive results because of dietary factors, and thus are more accurate if patients restrict their diets (see Table 34.1). Guaiac-based tests have the advantages of being relatively easy for patients and clinicians to use and relatively specific for lower gastrointestinal tract bleeding. The quantitative porphyrin tests are not affected by dietary factors and are potentially more sensitive than the other tests, depending on the cut point designated for a positive result. Recent evidence indicates, however, that at matched levels of specificity, the quantitative porphyrin tests are not significantly more sensitive than guaiac-based tests. Quantitative porphyrin tests have the potential disadvantages of not being specific for lower gastrointestinal tract bleeding and of requiring interpretation by a laboratory.

2.

Do not collect a stool sample from patients with hematuria or obvious rectal bleeding (eg, from hemorrhoids). Instruct women to avoid collecting stool samples during or just after a menstrual period.

3.

If possible, patients should avoid using medications that cause gastric irritation and bleeding for at least 48 hours before and during the testing period. Such medications include aspirin, nonsteroidal antiinflammatory drugs (NSAIDs), corticosteroids, anticoagulants, reserpine, antimetabolites, and chemotherapeutic agents. Consumption of excess amounts of alcohol should be avoided. The manufacturer of Hemoccult® recommends avoidance of aspirin and NSAIDs for 7 days before the test. When guaiac-based tests are used, patient adherence to the dietary guidelines in Table 34.1 for at least 48 hours before and during the testing period can help avoid false-positive and false-negative results. Despite previous reports, dietary iron does not cause false-positive test results. To prevent false-positive test results, avoid applying antiseptic preparations containing iodine to the anal area immediately before and during the testing period.

4.

When guaiac-impregnated cards are used, collect two separate samples from different sections of three consecutive bowel movements; use the supplied applicator and apply thin smears of the samples to the cards. Instruct patients to return samples as soon as possible for processing. Optimally, processing of the cards should occur within 6 days of collection but definitely not after 14 days. Rehydration of the samples with a drop of water before application of the developer increases sensitivity by approximately 30% to 40%, but it also decreases specificity by 2% to 3%, leading to significantly more false-positive results. For this reason, authorities disagree about the use of rehydration. A positive result on even one sample qualifies the entire test as positive. Store both cards and developer at room temperature, protected from heat and light.

5.

Patients who return samples through the mail should use special US Postal Service-approved envelopes. These may be obtained by contacting the manufacturers of the fecal occult blood test system.

6.

Because of the intermittent nature of bleeding in patients with colorectal cancer, malignancy cannot be conclusively ruled out by repeat fecal occult blood testing.

7.

Follow-up of a positive fecal occult blood test requires diagnostic procedures such as sigmoidoscopy, colonoscopy, or barium enema.

Table 34.1. Additional Instructions for Patients Using Guaiac-Based Tests.

Table

Table 34.1. Additional Instructions for Patients Using Guaiac-Based Tests.

Patient Resources

  • Colonoscopy: Questions and Answers; Colorectal Cancer: Questions & Answers; Polyps of the Colon and Rectum: Questions and Answers. American Society of Colon and Rectal Surgeons, 800 E Northwest Hwy, Suite 1080, Palatine, IL 60067; (708)359-9184.
  • What You Need to Know about Cancer of the Colon and Rectum. Office of Cancer Communications, National Cancer Institute, Bethesda, MD 20892; (800)4-CANCER; Internet address: http://cancernet.nci.nih.gov

Selected References

  1. Ahlquist DA, Wieand HS, Moertal CG, et al. Accuracy of fecal occult blood screening for colorectal neoplasia. JAMA . 1993; 269:1262–1267. [PubMed: 8437303]
  2. American Academy of Family Physicians. Summary of Policy Recommendations for Periodic Health Examination . Kansas City, Mo: American Academy of Family Physicians; 1997.
  3. American Cancer Society. Cancer Information Database. Atlanta, Ga: American Cancer Society; June 1997.
  4. American Cancer Society. Cancer Facts & Figures-1997 . Atlanta, Ga: American Cancer Society; 1997.
  5. American Cancer Society. Summary of American Cancer Society recommendations for the early detection of cancer in asymptomatic people. CA . 1993; 43:–.
  6. American College of Obstetricians and Gynecologists. Guidelines for Women's Health Care . Washington, DC: American College of Obstetricians and Gynecologists; 1996.
  7. American College of Obstetricians and Gynecologists. Routine Cancer Screening . ACOG Committee Opinion. Washington, DC: American College of Obstetricians and Gynecologists; In press.
  8. American College of Physicians. Guidelines. In: Eddy DM, ed. Common Screening Tests. Philadelphia, Pa: American College of Physicians; 1991:415-416.
  9. American College of Physicians. Suggested technique for fecal occult blood testing and interpretation in colorectal cancer screening. Ann Intern Med . 1997; 126:808–810. [PubMed: 9148657]
  10. American College of Physicians. Screening for colorectal cancer with the fecal occult blood test: a background paper. Ann Intern Med . 1997; 126:811–822. [PubMed: 9148658]
  11. Canadian Task Force on the Periodic Health Examination. Screening for colorectal cancer. In: The Canadian Guide to Clinical Preventive Health Care. Ottawa, Canada: Minister of Supply and Services; 1994: chap 66.
  12. Eddy DM. Screening for colorectal cancer. Ann Intern Med . 1990; 113:373–384. [PubMed: 2200321]
  13. Eddy DM, Ferioli C, Anderson DS. Screening for colorectal cancer. Ann Intern Med. In press.
  14. Fleischer DE, Goldberg SB, Browing TH, et al. Detection and surveillance of colorectal cancer. JAMA . 1989; 261:580–585. [PubMed: 2642563]
  15. Gnauck R, Macrae FA, Fleisher M. How to perform the fecal occult blood test. CA . 1984; 34:134–137. [PubMed: 6426710]
  16. Kewenter J, Bjork S, Haglind E, Smith L, Svanvik J, Ahren C. Screening and rescreening for colorectal cancer: a controlled trial of fecal occult blood testing in 27,700 subjects. Cancer . 1988; 62:645–651. [PubMed: 3292038]
  17. Knight KK, Fielding JE, Battista RN. Occult blood screening for colorectal cancer. JAMA . 1989; 261:587–593. [PMC free article: PMC1138865] [PubMed: 2491894]
  18. Levin B, Murphy GP. Revision in American Cancer Society recommendations for the early detection of colorectal cancer. CA . 1992; 42:296–299. [PubMed: 1515968]
  19. Mandel JS, Bond JH, Church TR, et al. Reducing mortality from colorectal cancer by screening for fecal occult blood. N Engl J Med . 1993; 328:1365–1371. [PubMed: 8474513]
  20. Macrae FA, St John JB, Caligiore P, Taylor LS, Legge JW. Optimal dietary conditions for Hemoccult® testing. Gastroenterology . 1982; 82:899–903. [PubMed: 7060911]
  21. Parker SL, Tong T, Bolden S, Wingo PA. Cancer statistics, 1997. CA . 1997; 47:5–27. [PMC free article: PMC1312878] [PubMed: 8996076]
  22. Pye G, Thomas WM, Hardcastle JD. Comparison of coloscreen self-test and Haemoccult faecal occult blood tests in the detection of colorectal cancer in symptomatic patients. Br J Surg . 1990; 77:630–631. [PubMed: 2200550]
  23. Ransohoff DF, Lang CA. Screening for Colorectal Cancer. N Engl J Med . 1991; 325:37–41. [PubMed: 1810273]
  24. Selby JV, Friedman GD, Quesenberry CP, Weiss NS. Effect of fecal occult blood testing on mortality from colorectal cancer: a case-control study. Ann Intern Med . 1993; 118:1–6. [PubMed: 8416152]
  25. Selby JV. How should we screen for colorectal cancer? JAMA . 1993; 269:1294–1296. [PubMed: 8437311]
  26. SmithKline Diagnostics. Product Instructions for Hemoccult® San Jose, Calif: SmithKline Diagnostics, Inc; 1994.
  27. US Preventive Services Task Force. Screening for colorectal cancer.In: Guide to Clinical Preventive Services. 2nd ed. Washington, DC: US Department of Health and Human Services; 1996: chap 8.
  28. Walter SD, Frommer DJ, Cook RJ. The estimation of sensitivity and specificity in colorectal cancer screening methods. Cancer Detect Prev . 1991; 15:465–469. [PubMed: 1782636]
  29. Winawer SJ, Fletcher RH, Miller L, et al. Colorectal cancer screening: clinical guidelines and rationale. Gastroenterology . 1997; 112:594–642. [PubMed: 9024315]
  30. Winawer SJ, Schottenfeld D, Flehinger BJ. Colorectal cancer screening. J Natl Cancer Inst . 1991; 83:243–253. [PubMed: 1994053]

Views

  • PubReader
  • Print View
  • Cite this Page

In this Page

Other titles in this collection

Recent Activity

ClearTurn OffTurn On

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...