Fecal Globin, Immunochemistry (InSure®)
Test Summary
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 in the United States, in men as well as women. According to American Cancer Society (ACS) estimates, 145,290 new cases of colorectal cancer will be diagnosed and more than 56,000 people will die of this disease in 2005, accounting for 10% of cancer deaths in each sex.1 The most common risk factor is age: >90% of colorectal cancers are diagnosed in people >50 years of age.1 Screening and early detection are crucial, as survival rates decrease dramatically with increasing cancer stage: 5-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 Although routine screening is recommended for average-risk individuals ≥50 years of age,3-5 fewer than half of age-eligible adults receive appropriate screening.6,7
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%.8 ACS guidelines indicate that a yearly FOBT is an acceptable screening method for average-risk individuals ³50 years of age; combining an annual FOBT with flexible sigmoidoscopy every 5 years is preferred over the use of either test alone.3
One drawback to the most common currently used FOBTs is that they are guaiac based; 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.7,9 Newer immunochemical assays such as InSure do not react with non-human hemoglobin or peroxidase, so food restrictions are not necessary. 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. Based on these features and published performance characteristics of immunochemical FOBTs, ACS guidelines suggest that immunochemical FOBTs such as InSure "are more patient-friendly, and are likely to be equal or better in sensitivity and specificity" relative to guaiac-based tests.3,10
Individuals Suitable for Testing
| • | Individuals undergoing routine screening for colorectal lesions or other sources of bleeding in the lower gastrointestinal tract |
Specimen Requirements
Samples should not be collected 1) during, or 3 days before or after, a menstrual period; 2) if bleeding hemorrhoids are present; 3) if there is visible blood in the urine or toilet bowl; 4) if there are bleeding cuts on the hands; or 5) if the toilet contains rust or saltwater. Toilet freshener should be removed and the toilet flushed prior to sample collection. Dietary roughage may increase test sensitivity, but no dietary changes or restrictions are required.
Method
| • | Immunochemistry | |
| – | Monoclonal, mouse anti-human hemoglobin-coated chromatography test strip | |
| – | Colorimetric detection | |
| • | Analytical sensitivity: 50 µg Hb/g feces11 | |
| • | Analytical specificity: specific for colorectal bleeding; does not detect blood from upper gastrointestinal tract9 | |
| • | Aliases: fecal immunochemical test; FIT; fecal occult blood test; FOBT; |
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| • | CPT code*: 82274 | |
Reference Range
Not detected
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.
Online Resources for Healthcare Professionals
| • | Obtain test ordering codes and specimen requirements from our online Test Menu. |
| • | Visit our Interpretive Guide, for information relating to test selection, utilization, and interpretation. |
| • | Simplify test ordering and results reporting with our connectivity solutions. |
| • | View this InSure information in a PDF format. |
| • | Visit www.insuretest.com for additional patient and healthcare professional information. |
Online Test Information for Your Patients
Your patients can learn about health conditions and laboratory tests in our online Patient Health Library. The library is founded on evidence-based information, and includes topics such as:
Your patients can also visit www.insuretest.com for additional information about the InSure test.
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* The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed.
References
1American Cancer Society. Cancer facts and figures 2005. Available at www.cancer.org/docroot/STT/stt_0.asp. Accessed Sept. 20, 2005.
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 Smith RA, Cokkinides V, Eyre HJ. American Cancer Society guidelines for the early detection of cancer, 2003. CA Cancer J Clin. 2003;53:27-43.
4 US Preventive Services Task Force. Screening for colorectal cancer: recommendations and rationale. AHRQ Pub. No. 03-510A. July 2002. Available at www.ahcpr.gov/clinic/3rduspstf/colorectal/colorr.pdf. Accessed July 18, 2003.
5 Winawer S, Fletcher R, Rex D, et al. Colorectal cancer screening and surveillance: clinical guidelines and rationale-update based on new evidence. Gastroenterology. 2003;124:544-560.
6 Centers for Disease Control and Prevention. Colorectal cancer test use among persons aged
7 Vernon SW. Participation in colorectal cancer screening: a review. J Natl Cancer Inst. 1997;89:1406-1422.
8 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.
9 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.
10 Levin B, Brooks D, Smith RA, et al. Emerging technologies in screening for colorectal cancer: CT colonography, immunochemical fecal occult blood tests, and stool screening using molecular markers. CA Cancer J Clin. 2003;53:44-55.
11 InSure Product Instructions. Falmouth, ME: Enterix Inc; 2000.
