Decrement in Hemoglobin Levels Is Indicative of Colorectal Cancer

Long-term variation in blood hemoglobin (Hb) levels could detect subtle gastrointestinal bleeding in the early development of colorectal cancer (CRC).

Anemia, a common blood disorder, is characterized by low Hb levels, and has long been associated with those suffering from CRC. A sharp decrease in Hb levels was thought to be a symptom of colon cancer.

In a recent study carried out at the School of Public Health, Tel Aviv University (Tel Aviv, Israel), a total of 1,074 CRC cases aged 45–75 years that had been diagnosed with CRC and had normal Hb levels were frequency matched for age and sex with cancer-free individuals at a ratio of 10 controls per case. In this retrospective study, the scientists looked at data from each participant's blood tests over a ten-year period, retrieved from a computerized database.

The scientists have discovered that it is the continuous long-term decline that may announce the onset of cancer. Though hemoglobin levels may vary in every human being as a result of aging, a distinct trend was discovered among study participants who had been diagnosed with colorectal cancer during the study period. Approximately four years prior to their diagnoses, their blood tests began to show a continuous decline in Hb levels. A declining trend of more than 0.28 g/dL every six months over a four-year period was observed and it may serve as a warning of illness on the horizon. CRC patients were characterized by an on-going, long-term, logarithmic decrement in Hb levels. Such small changes within the normal Hb range could be missed by health providers, but automatically detected by computerized alert algorithms. Participants of the study with colorectal cancer experienced a sharp decline in Hb levels, but because the declines did not put them outside the normal range, no red flags were raised.

Inbal Goldshtein, a graduate student and lead author of the study said, "In practice, a doctor will look at the final results and see if the hemoglobin levels are within a normal range, but this is not accurate enough. It is important to look at the continuing trend of each individual. If a person experiences a consistent decline relative to his own average level, it may be cause for concern." The study was published in the July 2010 issue of the European Journal of Cancer Prevention.

The benefit of this screening process is that can be part of an average physical. Current testing for colorectal cancer is often expensive and unpleasant and there is also a very low compliance rate among patients. The next step is to create an algorithm, which will automatically detect suspicious declines in Hb levels, advising physicians to send their patients for further testing. More than 50,000 people in the U.S.A. will die from colon cancer in 2010, but better screening could significantly reduce those numbers.

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