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Fecal Occult Blood Tests Offer Different Results

Immunochemical test holds advantages over guaiac test; finds more cancers, adenomas

MONDAY, July 28 (HealthDay News) -- The use of an immunochemical fecal occult blood test (I-FOBT) resulted in higher participation and detection rates for advanced adenomas and cancer than use of a guaiac-based fecal occult blood test (G-FOBT), according to research published in the July Gastroenterology.

Leo G. Van Rossum of the Radboud University Nijmegen Medical Center in Nijmegen, Netherlands, and colleagues analyzed data from both types of screening tools, which were sent on a randomized basis to 20,623 50- to 75-year-old individuals. Nearly 11,000 returned the tests -- 46.9 percent were G-FOBTs and 59.6 percent I-FOBTs.

In the G-FOBT group, 2.4 percent were positive, compared with 5.5 percent in the I-FOBT group. The guaiac test found 11 cancers and 48 advanced adenomas; the immunochemical test found 24 cancers and 121 advanced adenomas. The two options offer similar numbers-to-scope to find a single cancer, but G-FOBT significantly underestimates the prevalence of advanced adenomas and cancers in a screening population, the authors write.

"Another major advantage of the I-FOBT we used is that the test is semiquantitative. This allows shifting the cut-off value of the test. When resources are limited and the prevalence of CRC (colorectal cancer) in the population is expected to be low, one could consider increasing the cut-off value of the test and vice versa. In addition, the I-FOBT does not have dietary restrictions, because it is specific for human blood. In contrast, extensive dietary restrictions are advised for the G-FOBT to avoid false-positive test results, although others question this," the authors write.

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