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Fecal Globin by Immunochemistry (InSure)

Fecal Globin by Immunochemistry (InSure)

Test Summary

Fecal Globin by Immunochemistry (InSure®)

  

Clinical Use

  • Screen for lower gastrointestinal bleeding associated with colorectal cancer, adenomas, polyps, and other lower gastrointestinal conditions

Clinical Background

Colorectal cancer is the third most common form of cancer and the third leading cause of cancer death among both men and women in the United States. An estimated 143,000 new cases of colorectal cancer will be diagnosed and nearly 52,000 people will die of this disease in 2012.1 The most common risk factor is age: >90% of colorectal cancers are diagnosed in people older than 50.1

Screening and early detection are crucial, as survival rates decrease dramatically with increasing cancer stage. Five-year survival ranges from >90% for Dukes stage A to <5% for Dukes stage D. Moreover, detection and removal of precancerous polyps can reduce the incidence of colorectal cancer by 76% to 90%2 and mortality by more than half.3 Routine screening is recommended for average-risk individuals staring at age 50,4 but only 53% of screen-eligible adults receive appropriate screening.1

Because cancerous and precancerous colorectal lesions tend to cause low-level bleeding, assays for occult blood in feces have become an important screening tool. Annual screening with a fecal occult blood test (FOBT) can decrease colorectal cancer mortality by up to 33%.5 Current guidelines indicate that a yearly FOBT is an acceptable screening method for average-risk individuals age 50 and older. Combining an annual FOBT with flexible sigmoidoscopy every 5 years is preferred over the use of either test alone.4

FOBTs fall into 2 main categories, guaiac-based (gFOBT) and immunochemical. One drawback to gFOBTs is that they detect heme peroxidase activity and are not specific for human hemoglobin. Thus, hemoglobin from red meat, peroxidase from fruits and vegetables, and certain medications can cause false-positive reactions and need to be avoided for several days before the test. In addition, vitamin C (excess of 250 mg/day) from supplements or citrus fruits and juices may cause a false-negative guaiac test result. While these FOBTs are non-invasive and specimens can be collected at home, strict dietary and medication restrictions may decrease adherence.6,7

iFOBTs such as InSure do not react with non-human hemoglobin or peroxidase, minimizing the need for food restrictions. The lack of dietary restrictions, along with relatively simple “brush” sample collection of the stool specimen, may result in increased participation in FOBT screening.8,9 Immunochemical FOBTs are also more specific for lower gastrointestinal bleeding because they target the globin portion of hemoglobin, which does not survive passage through the upper gastrointestinal tract. Clinical studies have not found consistent differences in test performance between various immunochemical FOBTs and a sensitive available gFOBT.4 However, the InSure immunochemical FOBT was found to provide more sensitive detection of colorectal cancer and significant adenomas in a screening cohort, with a slightly higher false-positive rate.9

Individuals Suitable for Testing

  • Individuals undergoing routine screening for colorectal lesions or other sources of bleeding in the lower gastrointestinal tract

Method

  • Immunochemistry

   Monoclonal, mouse anti-human hemoglobin-coated chromatography test strip

   Colorimetric detection

  • Analytical sensitivity: 50 µg Hb/g feces10

  • Analytical specificity: specific for colorectal bleeding; does not detect blood from upper gastrointestinal tract6

  • Aliases: fecal immunochemical test; FIT; fecal occult blood test; FOBT; InSure®

Interpretive Information

Positive results indicate occult blood in the feces and should be followed up with physician consultation and possible endoscopic evaluation. Negative results indicate the absence of fecal blood; however, false-negatives can occur because of uneven distribution of blood in the feces or intermittent bleeding.

References

  1. American Cancer Society. Colorectal Cancer Facts and Figures 2012. Available at http://www.cancer.org/
    downloads/STT/CAFF2006PWSecured.pdf. Accessed October 29, 2012.

  2. Winawer SJ, Zauber AG, Ho MN, et al. Prevention of colorectal cancer by colonoscopic polypectomy. The National Polyp Study Workgroup. N Engl J Med. 1993;329:1977-1981.

  3. Zauber AG, Winawer SJ, O'Brien MJ, et al. Colonoscopic polypectomy and long-term prevention of colorectal-cancer deaths. N Engl J Med. 2012;366:687-696.

  4. Levin B, Lieberman DA, McFarland B, et al; American Cancer Society Colorectal Cancer Advisory Group; US Multi-Society Task Force; American College of Radiology Colon Cancer Committee. Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: a joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. CA Cancer J Clin. 2008;58:130-160.

  5. Mandel JS, Bond JH, Church TR, et al. Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study. N Engl J Med. 1993;328:1365-1371.

  6. Robinson MH, Pye G, Thomas WM, et al. Haemoccult screening for colorectal cancer: the effect of dietary restriction on compliance. Eur J Surg Oncol. 1994;20:545-548.

  7. Vernon SW. Participation in colorectal cancer screening: a review. J Natl Cancer Inst. 1997;89:1406-1422.

  8. Cole SR, Young GP, Esterman A, Cadd B, Morcom J. A randomised trial of the impact of new faecal haemoglobin test technologies on population participation in screening for colorectal cancer. J Med Screen. 2003;10:117-122.

  9. Smith A, Young GP, Cole SR, Bampton P. Comparison of a brush-sampling fecal immunochemical test for hemoglobin with a sensitive guaiac-based fecal occult blood test in detection of colorectal neoplasia. Cancer. 2006;107:2152-2159.

  10. InSure Product Instructions. Falmouth, ME: Enterix Inc; 2000.
     

Content reviewed 12/2012
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