Sarah is in her late 30s and has been having some gastrological problems. Her doctor referred her to a
specialist, whom he described as “widely recommended.” He examined her and ran some tests, including
the fecal occult blood test (FOBT). Surprised when one of the tests came back positive, this doctor
recommended a colonoscopy. He also assured Sarah there was no risk to the procedure.
In recent years, colonoscopy has become the standard procedure for detecting cancer or precancerous
polyps in the colon. Colonoscopy is an invasive procedure, requiring sedation while a flexible, tubular
instrument is inserted into the colon.
When Sarah asked her doctor whether the original test result could be flawed, he told her that there can
be a number of reasons an FOBT sometimes brings back false positive results. In order to get a second
opinion and clear her doubts about possibly having a colonoscopy unnecessarily, Sarah asked her doctor
to refer her to another gastroenterologist. After scheduling a new FOBT, her doctor handed her a list of
things she needed to avoid for three to five days before the test in order to prevent a false positive result.
These included:
- Eating red meat, fish, broccoli, potatoes, mushrooms, cantaloupe, grapefruit, carrots, cabbage,
cauliflower, radishes, Jerusalem artichokes and turnips - Eating iron-rich foods or taking iron supplements
- Taking acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs), such as aspirin or
ibuprofen - Supplements of 200 mg or more of vitamin C
As it turned out, Sarah had eaten some of the foods on the list, in addition to taking Vitamin C at six times
the dosage permitted for this test.
The main question that arises from this case is, “How many people undergoing FOBT tests are not
receiving this list from their doctor, and subsequently end up having a false positive test result which
makes them a candidate for colonoscopy?” I speculate that this applies to many or most patients.
On different note, a Canadian study reported in the Journal of the American Medical Association
(Volume 295, page 2366) confirms that a 10-year interval between colonoscopy screenings may be
appropriate for those who have had one negative procedure, meaning no cancer was found. Ten-year
screenings have long been recommended for detecting possible colon cancer, but the new research shows
that repeat screenings even after the ten years bear few or no benefits. Researchers studying cancer risks
at the University of Manitoba looked at records for nearly 36,000 patients who had negative screenings
for colon cancer between 1989 and 2003. They compared the incidence of colorectal cancer in this group
with that in the provincial population. The research team found that the risk of developing colon cancer
within less than 10 years of a negative colonoscopy was very low and remained lower beyond that time.
In fact, at 10 years, the risk of developing colon cancer was 72% lower. So much for the hype of making
colonoscopy every ten years a standard test for everyone.
Hypertension Produced In The Doctor’s Office?
If your visit to the doctor is accompanied by the fear of anticipating a serious physical problem, your
anxiety may trigger a stress response and raise your blood pressure. This phenomenon is known as
“white-coat hypertension.” While the doctor is measuring your blood pressure (using the old system of
measurement), the pressure of the inflating cuff against your blood vessels and the accompanying nerves
raises it even more. By the time the pressure in the cuff is lowered to read the pulsation level, you