Using monoclonal and polyclonal antibodies to detect only human blood in stool, this technology compares favorably when tested against other methodologies
New diagnostic technologies are literally tumbling out of research laboratories and biotech development companies at an increasing pace. The sheer volume of proprietary medical laboratory tests and new molecular diagnostic assays makes it a challenge for pathologists and clinical laboratory managers to identify which new lab tests have the greatest clinical value—and will also be adequately reimbursed by payers.
Each time a clinical laboratory wants to bring up a new medical laboratory test, it requires substantial effort. The laboratory will expend substantial financial, clinical, and operational resources to acquire the instrumentation, run the studies needed to validate the test, and begin the process of educating physicians about the value of the new test and how to use it in their medical practice.
New diagnostic technologies have transformed infectious disease testing over the past two decades. Rapid molecular tests, for example, make it possible for medical labs to deliver an accurate answer back to a referring physician in just hours—compared to the several days that are required for most long-standing microbiology test procedures. Now a similar transformation is underway in cancer testing. Two examples of how new technologies have revolutionized testing for specific types of cancers are lymphoma/leukemia and breast cancer.
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Colorectal Cancer
One type of cancer that is a high-profile target for improved diagnostic testing is colon cancer. It is one of the most common malignancies in men and women. The National Cancer Institute estimates that 141,210 new cases of colon and rectal cancers will be reported and an estimated 49,380 Americans will die of these diseases this year.
Pathologists and clinical laboratory managers know that regular screening tests can detect colorectal cancer early and help prevent cancer because some polyps can be identified and removed before they become cancerous. However, in recent decades the drawbacks associated with accepted screening methodologies for colon cancer have meant that most of the population is not screened for colon cancer according to the current standard of care.
The American Cancer Society (ACS) notes that colon cancer screening tests fall into two broad groups. The first group includes such diagnostic procedures as the flexible sigmoidoscopy, colonoscopy, double-contrast barium enema, and CT colonography (or virtual colonoscopy). By seeking abnormalities in the colon, these tests find both colorectal polyps and cancer, the society explained.
The second group of colorectal cancer screening procedures includes the range of lab tests performed by clinical laboratories. The American Cancer Society includes fecal occult blood (FOB) tests, fecal immunochemical tests, and stool DNA tests in this diagnostic group.
The problem with all of these tests is that they sometimes fail to detect polyps, the society said. The resulting false positive results are a challenge for patients and physicians because a false positive test result triggers more testing that increases the cost of care. False positive results also cause concern among patients.
Screening Tests for Colorectal Cancer
Given the high rate of colorectal cancer, the U.S. Preventive Services Task Force (USPSFT) recommends screening for colorectal cancer for adults aged 50 to 75 years using fecal occult blood testing, sigmoidoscopy, or colonoscopy even though the risks and benefits of these screening methods vary, the USPSFT said.
The issue of false-positive results is particularly difficult among patients who have had many cancer screens. An article published in the Annals of Family Medicine showed that the risk of obtaining a false-positive result from screening for prostate, lung, colorectal, and ovarian cancer is high and becomes cumulatively higher with ongoing screening. After 14 of these screening tests, the cumulative risk of a false-positive is 60.4% for men and 48.8% for women, the researchers reported.
Therefore, it was significant when Lab Tests Online (LTO) reported in an article, “Colon Cancer Stool Screening Tests Vary in Accuracy,” that the newer immunochemical screening tests that use antibodies to identify human blood in stool are more accurate than older screening tests based on chemical reactions.
LabTestsOnline.com cited the research of Sabrina Hundt, MSc; Ulrike Haug, Ph.D.; and Hermann Brenner, M.D., MPH, of The German Cancer Research Center, in Heidelberg, Germany. This research article, “Comparative Evaluation of Immunochemical Fecal Occult Blood Tests for Colorectal Adenoma Detection,” was published in the Annals of Internal Medicine, February 3, 2009.
Hundt, Haug, and Brenner wrote: “The various immunochemical fecal occult blood tests (iFOBTs) use different antibodies against human blood components. The authors compared characteristics of six qualitative iFOBTs and one guaiac-based FOBT to identify adenomas in adults who had screening colonoscopy.
Performance characteristics of the six iFOBTs varied widely: Sensitivity and specificity for detecting advanced adenomas ranged from 25% to 72% and 70% to 97%, respectively, compared with 9% and 96% for the guaiac test. Given these large ranges, choosing among available iFOBTs requires careful investigation.”
A new White Paper available at Dark Daily addresses the issues that healthcare providers follow when choosing screening tests for colorectal cancer. The report, Cleaning Up Your Laboratory’s FOB Testing Program: An Opportunity to Improve Patient Care, explains how the latest technology for iFOBT compares favorably to traditional testing. Using monoclonal and polyclonal antibodies to detect only human blood in stool, this technology has improved specificity, sensitivity, accuracy, the White Paper reported.
The White Paper discusses the two types of FOBT that are currently available. One is a chemical-based FOBT (CFOBT) that uses the chemical guaiac to detect heme (the iron- component in hemoglobin) in the patient’s stool. The other type is called immunochemical FOBT (iFOBT) and it uses antibodies to detect human hemoglobin protein in stool.
These two types of tests are explained in detail. The advantages of the iFOBT are compared to the CFOBT as they relate to pathologists, physicians, and patients. A case study in the White Paper includes statistics from the clinical laboratory at Jacobson Memorial Hospital in Elgin, North Dakota. This medical laboratory switched from a traditional guaiac test to the latest technology for iFOBT and specific benefits were realized by the lab, the hospital, and its patients.
Another case study presented in the White Paper is the experience of the clinical laboratory at Phoenix Indian Medical Center in Phoenix, Arizona. Phoenix Indian Medical Center evaluated different testing methods from multiple vendors before choosing the method the pathologists believed would be best for patient care.
In conclusion, the ability of new technologies to contribute to improved performance of assays used in screening individuals for colorectal cancer demonstrate how swiftly the standard of care in laboratory medicine can be changed for the better. New generation FOB lab tests are one example of the types of changes now occurring across the entire range of testing services offered by clinical laboratories and pathology groups.
—Joseph Burns
Related Material
Colon Cancer Stool Screening Tests Vary in Accuracy
False-positive Results Are Common with Cancer Screening
Comparative Evaluation of Immunochemical Fecal Occult Blood Tests for Colorectal Adenoma Detection
