What is being tested?
Calprotectin is a protein released by a type of white blood cell called a neutrophil. When there is inflammation in the gastrointestinal (GI) tract, neutrophils move to the area and release calprotectin, resulting in an increased level in the stool. This test measures the level of calprotectin in stool as a way to detect inflammation in the intestines.
Intestinal inflammation is associated with inflammatory bowel disease (IBD) and with some bacterial GI infections, but it is not associated with many other disorders that affect bowel function and cause similar symptoms. Calprotectin can be used to help distinguish between inflammatory and non-inflammatory conditions.
IBD is a group of chronic disorders characterized by inflamed and damaged tissues in the lining of the intestinal tract. The cause of IBD is not known, but these diseases are thought to be due to an autoimmune process that has been triggered by a genetic predisposition, a viral illness, and/or an environmental factor. The most common inflammatory bowel diseases are Crohn disease (CD) and ulcerative colitis (UC).
People with IBD typically have flare-ups of active disease that alternate with periods of remission. During a flare-up, a person may experience frequent bouts of watery and/or bloody diarrhea, abdominal pain, weight loss, and fever. Between these flare-ups, symptoms frequently subside. Many people may go through extended periods of remission between flare-ups. Calprotectin testing can be useful in monitoring disease activity. The test is not specific or diagnostic for IBD, but it may be done to detect and evaluate the degree of inflammation.
How is it used?
Calprotectin is a stool (fecal) test that is used to detect inflammation in the intestines. Intestinal inflammation is associated with, for example, some bacterial infections and, in people with inflammatory bowel disease (IBD), it is associated with disease activity and severity. The calprotectin test is not diagnostic but may be used to distinguish between IBD and non-inflammatory disorders and to monitor the severity of IBD.
A healthcare practitioner may order a calprotectin test to help investigate the cause of a person’s persistent watery or bloody diarrhea. The test may be ordered along with other stool tests, such as a stool culture to detect a bacterial infection, a test for ova and parasites (O&P), a stool white blood cell test, and/or a fecal occult blood test (FOBT). If a healthcare practitioner suspects inflammation, then a blood test that detects inflammation in the body, such as a C-reactive protein (CRP), or an erythrocyte sedimentation rate (ESR) if CRP is not available, may also be ordered. Testing is performed both to help determine what is causing a person’s symptoms and to rule out conditions with similar symptoms. This means that additional blood and stool testing may be performed depending on the suspected causes.
A calprotectin test may be ordered to help determine whether an endoscopy is indicated if IBD is suspected. A diagnosis of IBD is usually confirmed by performing an endoscopy (colonoscopy or sigmoidoscopy) to examine the intestines and by obtaining a small tissue sample (biopsy) to evaluate for inflammation and changes in tissue structures. This testing is invasive and is less likely to be necessary if inflammation is not present.
A calprotectin test may be ordered if a person with IBD has symptoms that suggest a flare-up, both to detect disease activity and to help evaluate its severity. For example, if a person has a moderately elevated calprotectin, then testing may be repeated several weeks later to see if it has stayed moderately elevated, increased, or returned to normal.
When is it ordered?
A calprotectin test may be ordered when a person has symptoms that suggest inflammation of the digestive system and when a healthcare practitioner wants to distinguish between IBD and a non-inflammatory bowel condition.
Signs and symptoms of IBD will vary from person to person and over time. They may include one or more of the following:
- Bloody or watery diarrhea
- Abdominal cramps or pain
- Weight loss
- Rectal bleeding
Testing for calprotectin may be performed when a healthcare practitioner wants to determine whether an endoscopy (colonoscopy or sigmoidoscopy) is likely or less likely to be necessary.
When a person has been diagnosed with IBD, a calprotectin test may be ordered whenever a flare-up is suspected, both to confirm disease activity and to evaluate its severity.
What does the test result mean?
An elevated calprotectin level is a person’s stool indicates that inflammation is likely present in the intestines but does not indicate either its location or cause. In general, the degree of elevation is associated with the severity of the inflammation.
Increases in calprotectin are seen with IBD, but also with bacterial infections, some parasitic infections, and with colorectal cancer. An endoscopy (colonoscopy or sigmoidoscopy) may be indicated as a follow-up test to help determine the cause of inflammation, signs, and symptoms.
In people newly diagnosed with IBD, concentrations of calprotectin may be very high.
A low calprotectin means that signs and symptoms are likely due to a non-inflammatory bowel disorder. Examples of these include viral infections in the digestive tract and irritable bowel syndrome (IBS). Unlike IBD, IBS does not cause inflammation. Rather, it causes cramp-like stomach pains and spasms with bouts of diarrhea and/or constipation. In people with low calprotectin results, an endoscopy is less likely to be indicated or useful.
A moderate calprotectin level may indicate that there is some inflammation present or that a person’s condition is worsening. A repeated calprotectin test with a result that is still moderately elevated or that has increased is likely to require further investigation and may warrant an endoscopy.
Is there anything else I should know?
Anything that causes inflammation in the intestines can cause an increase in stool calprotectin.
Calprotectin can be increased with the intestinal tissue damage and bleeding that is sometimes seen with use of non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen.
Calprotectin is related to another stool test, lactoferrin. Both are substances that are released by white blood cells in the stool and are associated with intestinal inflammation.
In some cases, calprotectin may be low even when inflammation is present (a false negative). This is most frequently seen with children.
Can a blood test be substituted for a stool calprotectin test?
What can I do to decrease my calprotectin?
Calprotectin is a reflection of gastrointestinal inflammation and is not affected by lifestyle changes. If it is due to an infection, then it will most likely return to normal when the infection resolves. If it is due to inflammatory bowel disease, then it will rise and fall with disease activity. In the rare case that an elevated calprotectin is caused by non-steroidal anti-inflammatory drug (NSAID) therapy, then it is likely to return to normal when the medication is discontinued.
How long will it take for my calprotectin results?
That depends on the laboratory performing the test. This test is somewhat specialized and is not offered by all laboratories. Your sample will likely be sent to a reference laboratory for testing and it may take several days before results are available.