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You’ve just had a checkup and a stool (fecal) test is done which is “positive,” meaning that there is blood detected in the stool. Or, your blood work shows a form of anemia that appears to be from iron deficiency. What do these mean and what to do? Below are some answered questions to help you understand this condition.

Condition Overview

The body normally keeps up a steady level in the amount of hemoglobin in the circulation, which is the chemical which makes blood red--it carries the oxygen around the body to all the tissues. A low level of hemoglobin is the condition of anemia. The red blood cells get produced in the bone marrow, typically live about 4 months then gets recycled.

Anemia happens for many reasons. Iron is a key ingredient needed to make hemoglobin, and a deficiency of iron will cause anemia. In adults, anemia from iron deficiency almost never comes from a bad diet, since there are so many foods with enough iron, and adults need only a tiny bit absorbed each day to stay in balance. Any time there is iron deficiency anemia then, we figure that there is usually a cause of blood loss behind it. This may be obvious or hidden (occult).

When obvious, the usual cause is menstrual and pregnancy blood loss in women, since we know many women don’t take in enough iron in their diet or in supplements to stay ahead. Rarely we see people who have large repeated losses of blood from nosebleeds or bleeding hemorrhoids, but it takes literally cups full of blood month after month to get anemic from these. In nearly everyone else who turns up with iron deficiency anemia, we are concerned they are losing blood from other causes, and this is usually a digestive tract problem. Occult bleeding--bleeding in which blood passes out the digestive tract--is detected by a chemical test on the stool (FOBT or fecal occult blood test). When the FOBT test is positive, it means there is digestive tract bleeding going on.

Why is it important?

Because an iron deficiency anemia or positive FOBT (occult blood test) or positive FIT (fecal immune hemoglobin test) may be the earliest or first indicator that a person has a cancer of the digestive tract, mostly in the colon. Many other things can do this too, but cancer is usually the most serious of the causes.

If a person is over 30 or 40 years old, how likely is cancer to be present?

When iron deficiency anemia is found and there is NO other good reason for it, after a medical history and physical is taken, as many as 10-20 % may be harboring a colon cancer they didn't know about. If an FOBT is positive (even just one of the 3 cards in a typical older guaiac kit like Hemoccult, or a single newer “FIT” or immune test like Hemassure), the risk is about 1-2 % (1 to 2 in 100 cases) that a colon cancer is a cause. That is why a careful investigation of the cause is advised.

We know that cancers detected before there are symptoms (like pain, obvious bleeding, weight loss, change in bowel pattern) have a much better outlook with treatment, a much greater chance of cure by surgery or of better life expectancy. That's why the FOBT is used in the first place as a screening or preventive test.

Iron deficiency anemia is more serious than a positive FOBT because it often means there has been digestive tract bleeding for many months or even years, often without a person being at all aware of it. We know that people who take aspirin frequently, or use anti-inflammatory drugs (ibuprofen, Naprosyn, diclofenac, and prescription "NSAIDs") may get stomach and digestive tract injury that may cause no symptoms yet cause the FOBT to react for blood or anemia to occur, but we can't assume it is the cause without proof, since patients growing polyps and cancers may be on these medicines too. Taking other blood thinners (warfarin/Coumadin, Pradaxa, Xarelto, Plavix/clopidogrel) don’t typically cause occult bleeding, but will dispose to much MORE blood loss because they prevent the blood from clotting and stopping the bleeding. They may unmask or make more obvious that something is wrong. Overt bleeding, or anemia, can occur when blood thinners are used in too high a dose or taken in combinations, such as aspirin with Plavix or Xarelto.

Types of Testing

CBC: Complete blood count; includes hemoglobin and other measures of the red cells, and numbers and types of white blood cells and platelets.
Men tend to run hemoglobin levels of 13-16, women 12-14. Anemia is any hemoglobin level below these, but sometimes-borderline levels aren't called anemia unless confirmed. There are literally many dozen types of anemia.

Iron: We can measure iron content directly in the blood, and also a test called ferritin that reflects the amount of iron stored up in the body. The "percent saturation" of iron tells us better whether the iron levels themselves are appropriate, low or high.

FOBT or FIT Fecal (stool) occult blood test: the chemical test run on a stool sample for bleeding, which is invisible but is occurring anyway. Usually done either during a digital rectal exam, or (much better yet) done at home with a tiny fecal sample applied to a card or put by a special brush into a container, and then returned to the labor office. A chemical is applied and reading taken, either Positive or Negative.

How urgent is testing?

It is always urgent to discuss the problem in detail, usually with the GI specialist, because we may be dealing with very serious causes. Sometimes the investigation can be put off 1 to several months, or taken a step at a time with other monitoring, but you should never make this decision without thorough medical advice.

What happens after testing?

If a cause of the problem is discovered, it depends on what turns up. If no cause is found, and the problem is anemia, then the minimum is to be sure you use enough iron to remedy the anemia and "refill the tanks" where iron is stored up. This usually means a full dose (300 or 325 mg, or 5 grain) iron tablet one to 3 times daily for 3-4 months. In all cases, it is important that the blood counts be rechecked periodically, and usually that another FOBT is run later.

What can cause positive FOBT tests or iron deficiency anemia?

MANY things. Swallowed blood sometimes gives a positive FOBT; bleeding ulcers, gastritis and esophagitis related bleeding; erosions within large hiatal hernias; benign colon polyps (which themselves may turn into cancer over several years), colitis disorders, fragile abnormal blood vessel malformations (in people over 70 especially; called angioectasia or angiodysplasia) may be the cause. False positive FOBTs do occur--that is, tests on the stool that turn positive but don't seem to actually be from digestive tract bleeding, even after a thorough investigation has taken place. In fact, of people investigated by detailed scope exam of the colon and/or stomach for a positive FOBT; who have no symptoms of a digestive problem, half of them have no cause found.

With the FIT-type of fecal test, these “false alarms” are much less, meaning a positive FIT has a much higher probability that some form of colon growth or bleeding source is present. This means that at least half or three-quarters of people with positive occult blood in stool DO have something of importance found to cause it, even if not cancer or polyps. There are rare cases of infections or of mal-absorption of iron causing anemia, but it is most unusual in the United States to have either of these. Diverticulosis, though common in older people, does not cause iron deficiency anemia and doesn't cause a positive FOBT. Diverticula can bleed rarely, but it is sudden, in large quantity and quite obvious.

What if only one FOBT is positive? Can't I just repeat the test?

How often we find serious things wrong seems the same if one test reacts, even just weakly positive, as if all 3 cards in a kit all react strongly. Bleeding is bleeding. We also know that even about half of the cancers and up to 90% of serious polyps will not bleed at any given time, which means an FOBT may show positive only sporadically, or not even at all, and a person can still have cancer or large/serious polyps. That's why iron deficiency must be checked into also, even if there seems to be no bleeding in the stool at that time. That's why we take even a single positive test seriously. That’s also why fecal tests are done yearly or every other year to be effective at detecting large polyps and cancers.

What if the workup is negative?

About 80-90% of the time, at least in adults who aren't still having menstrual bleeding, iron deficiency anemia will turn out to have an important proven cause; in the rest it may remain a mystery but usually the outlook is then quite good for full recovery and with a very small chance of a serious problem turning up later. If a positive FOBT is the reason for the investigation, and there is no anemia or iron deficiency, then about one half proves to have to serious cause, and the outlook is also ordinarily quite good.

If you believe in good preventive care, then you shouldn't feel bad that the testing was necessary or upset that no cause was found. We are always trying to improve the accuracy of preventive tests, but they will never be perfect at detecting only people with serious disease or of giving 100% assurance everything is fine.

How do we investigate?

The most thorough way and the way we usually recommend is to use a colonoscopy to examine the lower bowel and sometimes use an endoscope to examine the upper GI tract. Other brochures describe the tests in more detail. These are flexible fiberoptic thin tubes we can use to look directly through the entire upper or lower digestive tracts. They are usually done as outpatient examinations, under a sedative given through an intravenous so that you have minimal awareness of the procedure going on, and these exams have an excellent safety record. At times the testing may be more limited if we judge it likely there are simpler explanations for the problem that we can confirm by simpler tests.

If we believe occult bleeding may be coming from the small intestine, we have a “capsule camera” test which may find these unusual problems.

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