A BOWEL cancer test which checks for hidden blood in stools could be used to flag up people at risk of premature death from all causes, a new study suggests.

Around half of people who screen positively for blood using the faecal occult blood test (FOBT) do not end up having bowel cancer.

However, a study by Dundee researchers has found that even within this group, a positive FOBT result was associated with a 58 percent heightened risk of death from all causes.

In particular, they found that it was associated with a heightened risk of dying from circulatory, respiratory, digestive, blood, hormone and neuropsychological diseases, as well as other types of cancer.

In an article published today in the BMJ journal, Gut, they suggest that FOBT "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".

The study was led at the Medical Research Institute in Ninewells Hospital, Dundee, by cancer screening expert Professor Robert Steele, who is also the chair of the UK National Screening Committee.

Previous research has indicated that stool blood might predict life expectancy, independent of its association with bowel cancer.

However, potentially influential factors, including drugs such as aspirin that might predispose patients to internal bleeding were not accounted for.

To try and address this, the researchers drew on linked prescribing, bowel cancer screening, and death registry data for nearly 134,000 people aged between 50 and 74 in Tayside from March 2000 to the end of March 2016.

In total, 2714 people tested positive for blood during this period. Their survival was tracked from the date of this first test until death or the end of March 2016, whichever came first.

Overall, people who had a positive FOBT result were nearly eight times as likely to die of bowel cancer as those who tested negative, after taking account of gender, age, deprivation, and drug treatment.

More surprising was that a positive FOBT result was also associated with a 58 percent heightened risk of death from all causes other than bowel cancer.

Even after adjusting for age, gender and deprivation, a positive FOBT result was still strongly associated with early death.

The researchers stress there are no obvious explanations for their findings at this stage.

In Scotland, the FOBT bowel screening kit was replaced in November 2017 by a simpler test known as the faecal immunochemical test (FIT), which is better at detecting how much blood is present in a stool sample.

In a linked commentary to the Gut article, Professor Uri Ladabaum of Stanford University School of Medicine, writes that hidden stool blood “may be telling us more than we might have thought".

He adds: “If occult blood in faeces is a predictor of life expectancy and multiple [non-bowel cancer] causes of death, the inevitable next questions concern the implications for organised [bowel cancer] screening programmes or opportunistic [bowel cancer] screening.”