• Calprotectin is a protein made by your white blood cells. It is released when white blood cells trap and ingest harmful bacteria, viruses, and fungi. Calprotectin also signals to other cells to start the inflammation process.
• Inflammation is an important part of the healing process, increasing blood flow to the area.
• If you have inflammatory bowel disease (IBD), the cells in the lining of your intestines become inflamed and release calprotectin.
• Some calprotectin is absorbed into your faeces (stool).
• Measuring the amount of calprotectin in the stool can show whether there is inflammation and if so, how severe it is.
• The test is useful in helping to distinguish between IBD and non-inflammatory bowel conditions.

Calprotectin is a protein that is made by the white blood cells in your immune system when there is inflammation. When it occurs in the intestine some of the protein 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 your intestine and tell how severe it is.

The test is useful in helping to 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 your stool is likely to be due to IBD.

If the test comes back with a normal or low level it is most likely due to irritable bowel syndrome (IBS), a condition that causes altered bowel habits when there is no inflammation.

Calprotectin levels cannot be used to explain the cause of the IBD. Further blood tests, imaging, or endoscopy (a test where a camera looks inside your body) are needed for this. Calprotectin is also a very useful test for monitoring IBD flare-ups.

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 possibly poisonous substances.

The lining of the intestines is designed to manage this with some cells in the lining activating inflammation and others turning it off. In someone with 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, which are a type of white blood cell that are responsible for managing inflammation. When there is inflammation in the intestines, neutrophils come to that area, 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 evaluate the amount of inflammation.

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

You will need to have 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 (in which a camera looks inside the bowel) 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 during which they have periods of inflammation and pain. Calprotectin testing is used to evaluate the degree of inflammation and can help avoid the need for a surgical biopsy to monitor IBD.

Sample

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

Any preparation?

None.

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 (bowel) 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 tests and need an endoscopy.

Reference intervals - comparing your results to the healthy population

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

• Reference intervals are the range of results expected in healthy people.
• They are used to provide a benchmark for interpreting a patient's test results.
• When compared against them, your results may be flagged high or low if they sit outside this range.
• Some reference intervals are harmonised or standardised, which means all labs in Australia use them.
• Others are not because for these tests, labs are using different instruments and chemical processes to analyse samples.
• Always compare your lab results to the reference interval provided on the same report.

If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation.

Reference intervals for calprotectin faeces vary between labs so you will need to go through your results with your doctor. Your doctor is the best person to interpret your results.

• The cause of IBD is not known but is thought to be due to an autoimmune process that has been triggered by genetic factors, a viral illness and/or environmental factors.
• 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 often 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.

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?

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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