Summary

Calprotectin is a protein that is produced by the immune system when inflammation is present. When it occurs in the intestine it is absorbed into the faeces (stool). By measuring the amount of calprotectin in the stool it is possible to show whether there is inflammation in the intestine and to assess its severity. The test is useful in helping distinguish between inflammatory bowel disease (IBD) such as Crohn’s disease or ulcerative colitis and non-inflammatory bowel conditions that cause similar symptoms. A high level of calprotectin in the faeces is likely to be due to inflammatory bowel disease (IBD). If the test comes back with normal or low level it is most likely due to irritable bowel syndrome (IBS), a condition that causes altered bowel habits with no inflammation. Calprotectin levels cannot be used to determine the cause of the IBD and several other tests will be needed for this diagnosis. It is also a very useful test for monitoring IBD flare ups.

Why get tested?

Inflammation is an important part of the body’s immune response to potentially harmful substances – it starts the healing process. It occurs naturally in the intestines as a part of dealing with unwanted bacteria and potentially poisonous substances. 

The lining of the intestines is designed to manage this with some cells activating inflammation and others turning it off. In someone with inflammatory bowel disease (IBD) such as Crohn’s disease or ulcerative colitis, the system is not working properly, and constant inflammation damages the walls of the intestine, which over time becomes worse.

Calprotectin is a protein released by neutrophils a type of white blood cell that are responsible for managing inflammation. When there is inflammation in the intestines neutrophils start to accumulate and calprotectin is released into the faeces. The more inflammation, the greater the number of neutrophils and the greater the amount of calprotectin released into the faeces.  By measuring the level of calprotectin in a stool sample, it is possible to assess the amount of inflammation.  

The calprotectin test can help distinguish between inflammatory bowel disease (IBD) and other non-inflammatory conditions that cause similar symptoms.  However, it cannot diagnose Crohn’s disease or ulcerative colitis. 

You will need to have several other tests to check for inflammation and rule out infections, parasites and other conditions. The calprotectin 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 faecal occult blood test (FOBT).  A blood test that detects inflammation in the body may be needed, such as a C-reactive protein (CRP), and/or an erythrocyte sedimentation rate (ESR).

The gold standard test for IBD is a colonoscopy and tissue biopsy where a small sample of your intestine is removed and assessed under a microscope for inflammation changes in the tissue structures. 

Measuring calprotectin levels is useful to monitor someone with IBD. People with IBD typically have flare-ups of active disease that alternate with periods of remission. Calprotectin testing is used to evaluate the degree of inflammation and can help avoid the need for a surgical biopsy to monitor  IBD.

Having the test

Sample

Stool (faeces) A stool sample must be collected in a clean container provided by the laboratory. This sample should not be uncontaminated by urine or water.

Any preparation?

None.

Your results

Reading your test report

Your results will be presented along with those of your other tests on the same form.  You will see separate columns or lines for each of these tests.  

• A raised calprotectin indicates that inflammation is likely to be present but does not indicate either its location or cause. In general, the higher the level, the greater 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 needed as a follow-up test to help decide on the cause of inflammation,  and your 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 irritable bowel syndrome (IBS) and viral gastrointestinal infections. 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 raised or that has increased further is likely to require more investigation and may warrant an endoscopy.

Reference Intervals

Your results will be compared to reference intervals (sometimes called a normal range). 

• Reference intervals are the range of results expected in healthy people 
• When compared against them your results may be flagged high or low if they sit outside this range
• Many reference intervals vary between labs so only those that are standardised or common across most laboratories are given on this website.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.

Reference intervals for calprotectin vary between labs so you will need to go through your results with your doctor.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms.   It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

Any more to know?

• The cause of IBD is not known, but is thought to be due to an autoimmune process that has been triggered by a genetic predisposition, a viral illness, and/or an environmental factor. 
• Anything that causes inflammation in the intestines can cause an increase in stool calprotectin.
• 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. The clinical use of these tests is still relatively new. 
• In some cases, calprotectin may be low even when inflammation is present (a false negative). This is most frequently seen with children.
• There is no Medicare rebate available for the faecal calprotectin test so you will need to pay the full cost of the test. This cost varies between laboratories.

More information

Pathology and diagnostic imaging reports can be added to your My Health Record. You and your healthcare provider can now access your results whenever and wherever needed.
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