Fecal occult blood linked to death from diseases other than CRC

A positive fecal occult blood test (FOBT) indicates a higher risk of death from colorectal cancer (CRC), but a new study found it’s also associated with increased risk for death from a wide range of other chronic diseases.

“This is the first observational study to demonstrate a link between fecal bleeding and increased risk of death from a range of diseases other than colorectal cancer,” said lead author Robert Steele, MD, professor of surgery, Division of Cancer, University of Dundee Medical School, Dundee, Scotland.

The study results, recently reported in the journal Gut, showed that a positive FOBT was significantly associated with increased mortality risk for death from circulatory, respiratory, digestive, neuropsychological, and blood and endocrine diseases, as well as non-colorectal cancers.

In 2000, Scotland established a screening program using the guaiac fecal occult blood test (gFOBT), which reduced mortality from CRC by up to 27%. But screening results came out false positive for “quite a number of patients” who weren’t diagnosed with colorectal cancer, Dr. Steele said.

“We were always curious as to why this should be, so we went back to the early cohorts to examine outcomes for those with positive compared to negative FOBT results,” he explained.

The current study involved more than 134,000 individuals who participated in gFOBT screening in Tayside, Scotland, from March 2000 (when the screening program began) to March 2016. The researchers reviewed their test results in comparison with mortality data, and adjusted for gender, age, deprivation quintile, and medication that can cause bleeding.

Results showed that the 2,714 individuals who tested positive had a higher risk for death from CRC (HR 7.79, 95% CI 6.13-9.89, P < 0.0001) and from all non-CRC causes (HR 1.58, 95% CI 1.45-1.73, P < 0.0001), than those who tested negative.

“What we found that is that if you had a positive test, you were more likely to die from colorectal cancer, which is what we expected, but we also found that all-cause mortality was higher,” Dr. Steele said. “We then linked this data with specific causes of death and found that the risk of dying from a series of other diseases such as heart attacks, circulation disorders, respiratory disease, and many other cancers was also higher.”

Why would fecal occult blood be associated with, say, a heart attack? It’s not clear why or how just yet, Dr. Steele said. “But we think that it might be related to levels of inflammation throughout the body as this is a marker of general ill health, and chronic inflammation is a driving factor behind whole series of whole host of other diseases,” he said. “In any event, if someone is found to have unexplained blood in their feces, it may mean that they are at risk of developing chronic disease and may benefit from attention to their lifestyle.”

The next step in this line of research will be prospective studies to find a link between lifestyle diseases and fecal bleeding. “If hemoglobin in feces is a risk factor for all-cause death, it may have potential as a modifiable biomarker that could be used to assess the efficacy of both lifestyle and drug interventions to reduce the risk of premature mortality,” Dr. Steele and coauthors predicted.

This study was funded by the Chief Scientist Office of the Scottish Government Health Department.