Immunological Tests Are Superior for Colon Cancer Screening
22 Jul 2013
The fecal immunochemical tests (FITs) for hemoglobin offer a number of advantages over traditional guaiac based fecal occult blood tests (gFOBTs).
The major advantage seems to come at the price of higher positivity rates and lower specificity and hence a higher load of work-up colonoscopies, which makes a final judgment of the superiority of either test difficult.
Scientists from the German Cancer Research Center (Heidelberg, Germany) compared three quantitative FITs with a gFOBT among participants of the German screening colonoscopy program. They obtained stool samples and colonoscopy reports from 2,235 participants of screening colonoscopy from 2005 to 2009. Patients willing to participate were given stool collection instructions and devices, including a small container and one test card for a gFOBT (HemOccult, Beckman Coulter; Krefeld, Germany).
The stored stool samples were assayed with two automated, enzyme-linked immunosorbent assay (ELISA) based FITs, RIDASCREEN Haemoglobin, and RIDASCREEN Haemo-/Haptoglobin Complex, (R-Biopharm AG; Darmstadt, Germany). Cut-offs for positivity was 2 μg hemoglobin per gram stool. The stool samples were further analyzed, including a third FIT, OC-SENSOR, (Eiken Chemical; Tokyo, Japan).
The enzyme-based test detected one third of all colon cancer cases, about 9% of advanced precancerous adenomas lesions, and about 5% of early precancerous lesions. In 95 out of 100 participants with negative test results, no tissue abnormalities were found in the subsequent colonoscopy. Despite the already high specificities of the gFOBT for all outcomes, ranging from 95.2% to 95.4%, specificities were even higher for each of the FITs and each outcome. With estimates between 96.8% and 97.8%, specificities with respect to the detection of any cancer or any advanced neoplasm were very high for all three FITs.
Hermann Brenner, MD, MPH, a professor of clinical epidemiology, and senior author of the study said, “For the first time we have shown by direct comparison that the diagnostic performance of immunological stool tests is significantly higher than that of the enzymatic test at the same rate of positive results. Tests for occult blood in the stool will continue to be an important part of colon cancer screening. We therefore recommend including immunological tests in cancer screening programs in Germany. Many more people would thus benefit by obtaining a life-saving clue pointing to a hidden case of cancer.” The study was published on May 22, 2013, in the European Journal of Cancer.