Gut
Alfa-1-Antitrypsine
A blood protein in the stool; a measure of protein loss through the gut wall, used in hospital for a specific question.
Everything about this testWhat it measures
Alpha-1 antitrypsin is a protein from the liver that circulates in the blood. It is hardly broken down in the gut. If blood proteins leak into the gut through a damaged or inflamed gut wall, alpha-1 antitrypsin ends up in the stool. According to the Dutch Society for Clinical Chemistry (NVKC), it is not present in the stool of healthy people; the amount is a measure of protein loss through the gut.
- Protein loss through the gut (protein-losing enteropathy), for example in a chronic inflammation of the bowel such as Crohn's disease
High
A raised value means that protein from the blood is being lost through the gut wall. This may fit a chronic inflammation of the bowel such as Crohn's disease, celiac disease, an intestinal infection or a problem with the drainage of lymph fluid from the gut. Symptoms that fit this are long-lasting diarrhea, weight loss and fluid retention (swollen ankles) due to a low protein level in the blood. Blood in the stool, including menstrual blood, raises the value without there being any protein loss.
Low
A low or undetectable value is the usual result and means that there is no measurable protein loss through the gut. A low value in the stool says nothing about an inherited deficiency of alpha-1 antitrypsin; that is measured in the blood.
If your result is abnormal
With an abnormal result without symptoms, no follow-up is usually needed. With bowel symptoms, the GP can request calprotectin in the stool and blood tests, and refer you to a gastroenterologist if there are signs of a chronic inflammation of the bowel.
Reliability
According to the Dutch Society for Clinical Chemistry (NVKC), alpha-1 antitrypsin in the stool is used as a measure of protein loss through the gut, mainly in hospital with unexplained weight loss and a low protein level in the blood. How often a raised value occurs in people without symptoms, and what it then means, has not been well studied. A raised value does not say which bowel condition is the cause.
Limitations
- Blood in the stool, including menstrual blood or blood from hemorrhoids, raises the value.
- A single stool sample is less reliable than stool collected over several days.
- Measurement methods and cutoff values differ per laboratory.
How common is this
Bowel symptoms are common: according to the guideline, irritable bowel syndrome affects about 4 in 100 adults in the Netherlands. Chronic inflammatory bowel diseases such as Crohn's disease and ulcerative colitis are much rarer; the guideline gives no Dutch figure for them. How often an abnormal result for these markers occurs in people without symptoms is not known.
Who is this useful for
In people without symptoms, an abnormal result says little, because the meaning has not been established and a passing infection or a painkiller can raise the value. With long-lasting diarrhea or abdominal symptoms, the GP uses calprotectin in the stool to rule out a chronic inflammation of the bowel, and a blood test if celiac disease is suspected. With blood in the stool, unintended weight loss, diarrhea at night or new bowel symptoms after age 50, this test is no substitute for a visit to the GP.
Sources
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results