A calprotectin stool test detects levels of calprotectin, which is a protein that indicates bowel inflammation, in a person’s stool. Although doctors typically perform these tests to help diagnose inflammatory bowel disease (IBD), they may also use them to track the development of an existing IBD diagnosis.
A calprotectin stool test, or a fecal calprotectin test, checks for inflammation in the intestines. With this type of test, a laboratory examines a person’s stool sample for calprotectin, which is a type of protein, to determine inflammation levels in the intestines.
If a person is experiencing symptoms that indicate an issue with the intestines, a calprotectin stool test can help doctors tell the difference between inflammatory and noninflammatory causes. Bacterial infections can cause inflammation, as can IBD.
It is important to note that calprotectin test results are more representative of inflammation in the colon than inflammation in the small intestine. This means that the test cannot always accurately detect all forms of IBD. Crohn’s disease, for example, may only affect the small intestine.
This article will look at how the calprotectin stool test works, when a person may take one, and what to expect while doing so.
Neutrophils are a type of white blood cell. If a person has any inflammation in the gastrointestinal (GI) tract, neutrophils travel to the area of inflammation. They then release calprotectin, which is a protein. This release of calprotectin causes higher levels of the protein in the person’s stool.
A calprotectin stool test measures the amount of calprotectin in the stool to show how much inflammation is present in the intestines.
A calprotectin stool test is noninvasive, and people only have to provide a stool sample. The laboratory will provide a clean container for the sample. There should be no urine or water present, as this could contaminate the sample.
A doctor may request a calprotectin stool test if a person has symptoms that could indicate that they have IBD. Such symptoms include:
- watery diarrhea
- bloody diarrhea
- cramps or pain in the abdomen
- unintentional weight loss
- bleeding from the rectum
- weakness or fatigue
A calprotectin stool test can help a doctor find out if a person has IBD or a noninflammatory bowel condition, such as irritable bowel syndrome (IBS).
Doctors may also use a calprotectin stool test for a person who has already received a diagnosis of IBD. They can use the test to check if their inflammation levels have decreased in order to find out if their treatment plan is working effectively.
They may also use a calprotectin stool test if a person has an IBD flare. This can help them determine how severe the person’s levels of inflammation are compared with their baseline levels.
Once the laboratory receives the stool sample, it will test calprotectin levels using a method called enzyme-linked immunosorbent assay (ELISA).
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An ELISA test can detect substances such as:
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The article also notes that, in some cases, a person may be able to carry out a calprotectin stool test at home. They can use a sampling device to extract the correct amount of sample for testing. They can then use an app on their smartphone to analyze the results.
However, test reliability may vary depending on the manufacturer of the kit.
According to the same 2017 article above, normal and abnormal ranges of calprotectin are generally as follows:
- Calprotectin levels of 50–200 micrograms per milligram (μg/mg) are usually normal. This level may indicate a slight elevation of calprotectin levels, but it is not usually enough to warrant further investigation.
- Calprotectin levels higher than 200 μg/mg may indicate an inflammatory condition.
- Calprotectin levels of 500–600 μg/mg will almost definitely indicate an inflammatory condition.
It is important to note that normal and abnormal ranges of calprotectin can vary between different test kits and by location due to sanitation and the prevalence of intestinal infections.
A doctor may recommend a calprotectin stool test for two main reasons: to diagnose a condition or to monitor an existing one.
When diagnosing a condition
A person may need a calprotectin test if they have any symptoms that could indicate inflammation in the intestines. These symptoms include:
- frequent diarrhea
- abdominal pain
- bloody stool
- weight loss
When monitoring an existing diagnosis
A doctor may also use a calprotectin test if a person already has IBD. By showing levels of inflammation, the test can help the doctor monitor the condition, find out if treatment is working, or determine the severity of a flare.
A calprotectin stool test is a noninvasive test. There is no need for any preparation of the bowel beforehand.
Usually, a doctor will collect a stool sample from the person and send it away to a laboratory to test. Some doctors or laboratories may provide a person with instructions on how to collect the sample at home. The laboratory will also provide a clean container for the sample to prevent any potential contamination. The person must make sure that the stool sample does not contain any urine or water.
The doctor will then notify the person once they receive the results of the test. After interpreting the results, they may carry out further testing if the results show moderate-to-high levels of inflammation.
If a person has low or normal calprotectin levels, it may signify that there is no inflammation in the colon or that a noninflammatory condition may be causing symptoms.
The time frame for test results will vary depending on the laboratory carrying out the test. After the laboratory tests the stool sample, it may take several days for the results to become available.
If a person has taken a home test, they may receive their test result within a few hours.
Low or normal calprotectin levels may signal a noninflammatory bowel condition, such as IBS, or a viral infection in the GI tract.
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Moderate calprotectin levels, or levels that have increased from one test to the next, could be a sign of inflammation or the worsening of a condition. A doctor may choose to carry out further testing to investigate. This may take the form of endoscopy.
A calprotectin stool test is a noninvasive test to measure calprotectin levels in a person’s stool sample. Levels of calprotectin, which is a type of protein, in the stool can indicate levels of inflammation in the intestines.
A person may require a calprotectin stool test if they have symptoms of inflammation in the intestines, such as frequent diarrhea, stomach pain, or bloody stool.
The results of a calprotectin stool test can help a doctor determine whether a person has an inflammatory or noninflammatory condition of the intestines. They may also use a calprotectin stool test to monitor an existing IBD diagnosis.