Fecal Blood Test Predicts Lower Gastrointestinal Lesions

The immunochemical fecal occult blood test (iFOBT) is effective for predicting lesions in the lower intestine but not in the upper gastrointestinal (GI) tract.

The iFOBT is a useful noninvasive tool to screen for bleeding without symptoms in the lower GI tract and if bleeding is discovered, a colonoscopy is then used to investigate the source of bleeding.

Scientists at the National Taiwan University (Taipei, Taiwan) assessed the specificity of iFOBT, looking at a group of 2,796 people including 1,654 men and 1,142 women, who underwent voluntary bidirectional endoscopies and an iFOBT. The mean age of the participants was 49 years who were all asymptomatic of bleeding and of major GI disorders. They had an iFOBT, blood tests, colonoscopy and an upper GI tract endoscopy, as well as being interviewed.

A one-step commercial iFOBT kit with a brush-type sampler (OC-Light, Eiken Chemical Co. Ltd., Tokyo, Japan) was given to all participants. This test has a positive cutoff level of 50 ng/mL. Of the total participants in the study, 397 people (14.2%) had a positive iFOBT result, indicating bleeding. The iFOBT was specific for almost 90% of colorectal cancers, adenomas, and important lower GI lesions. Lower GI lesions were more common (24.1%) compared with those in the upper GI tract (17.9%). Lesions in the lower GI tract were more frequent in iFOBT-positive screens than in negative screens (41.3% versus 21.3%), whereas the frequency of lesions in the upper GI tract was similar in both positive and negative screens.

The authors concluded that the specificity of the iFOBT was almost 90% for predicting colorectal cancer, adenoma, or any important lesion in the lower gastrointestinal tract. Among participants who had a negative colonoscopy, a false-positive result of the immunochemical fecal test was associated with the use of antiplatelet drugs and a low hemoglobin concentration. The overall findings show that the immunochemical fecal test can be used as a specific diagnostic tool. The study was published on August 2, 2011 in the Canadian Medical Association Journal (CMAJ).

Related Links:
National Taiwan University
Eiken Chemical Co. Ltd.