Health
Immunochemical tests found better than guaiac for fecal occult blood
■ Newer tests are more sensitive and more specific in detecting blood in the stool, according to a new study.
By Susan J. Landers — Posted Feb. 17, 2009
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Washington -- Immunochemical fecal occult blood tests are worth a closer look by physicians interested in low-cost screening options for colorectal cancer, a new study suggests. These tests may be more accurate and have fewer restrictions than the more widely used guaiac-based screens.
German researchers compared the performances of six immunochemical FOBTs among adults who were about to receive screening colonoscopies with one guaiac-based version of the test. The results of the study are in the Feb. 3 Annals of Internal Medicine (link).
The researchers found the detection abilities of the immunochemical FOBTs varied markedly. However, the investigators also concluded the tests were better able to detect precursor lesions than were the guaiac-based tests.
Colorectal cancer is now the third most common cancer in the world, causing about 500,000 deaths each year, the researchers note. But the disease can be prevented if precancerous lesions are detected early and removed.
Randomized controlled trials have shown the guaiac-based tests can aid preventive efforts when positive tests are followed by colonoscopy and removal of the lesions. However, these tests are not specific for human hemoglobin and can produce false readings from, for example, traces of red meat or vitamin C in the stool.
The immunochemical tests, which use specific antibodies against components in human blood, overcome this problem, write the researchers.
A switch to the immunochemical tests makes sense because of their improved sensitivity and specificity, said Thomas Imperiale, MD, professor of medicine at the Indiana University School of Medicine Melvin and Bren Simon Cancer Center. "Even upper GI blood is missed by the tests," he added. Dr. Imperiale did not have a role in the study.
"We have done tons of colonoscopies on people who have false-positive fecal occult blood tests because they don't restrict their diets or they don't stop taking their baby aspirin," he said.
The researchers received stool samples from 1,319 men and women who were undergoing screening colonoscopies at 20 centers in Germany. The FOBTs were conducted on stool samples collected before bowel preparation.