What is faecal calprotectin?

A simple guide to one of the most common stool tests used to monitor inflammation in children with IBD.

If your child has IBD, you may have heard their healthcare team talk about faecal calprotectin, sometimes shortened to calprotectin or FC.

The name sounds complicated, but the idea behind the test is quite simple.

Faecal calprotectin is a protein that can be measured in poo. When there is inflammation in the bowel, the amount of calprotectin can increase.

This makes it a useful tool for helping your child's IBD team understand what is happening inside the bowel.

Why is my child's doctor checking it?

One of the tricky things about IBD is that symptoms don't always tell the whole story.

Your child might feel well while there is still some inflammation present. Equally, tummy pain or diarrhoea doesn't always mean that IBD inflammation is the cause.

Faecal calprotectin gives the healthcare team another piece of information.

It can help them:

• Look for evidence of inflammation in the bowel

• Assess how active IBD may be

• Monitor how well treatment is working

• Look for changes over time

• Help decide whether further investigation may be needed

• Monitor children who have previously had active disease

It is usually considered alongside your child's symptoms, examination, blood tests and other investigations rather than being used on its own.

What exactly is calprotectin?

Calprotectin is a protein found inside certain types of white blood cells.

When inflammation occurs in the bowel, these cells can move into the intestinal lining and release calprotectin.

Some of that calprotectin passes into the stool.

A laboratory can measure the amount of calprotectin in a stool sample.

More calprotectin can suggest more inflammation — but it doesn't tell you exactly what is causing the inflammation.

How does my child collect the sample?

The test requires a small sample of poo.

Your child's healthcare team or pathology laboratory will provide instructions and a collection container.

Usually, the important thing is to make sure the sample is collected as instructed and doesn't become contaminated with urine or toilet water.

It can feel awkward at first, particularly for an older child or teenager, but it's a very routine test for children with IBD.

If your child is embarrassed about collecting the sample, help them and reassure them that this is a normal part of monitoring their condition.

What does the result mean?

Your child's result will usually be reported as a number, often in micrograms per gram (µg/g).

Generally, a higher result suggests more intestinal inflammation.

But there isn't one number that can tell you:

Different laboratories and clinical situations can use different reference ranges, and the result needs to be interpreted in context.

Your child's IBD team will consider the result alongside their symptoms, previous results and other tests.

A low result

A low faecal calprotectin result generally suggests that there isn't a significant amount of intestinal inflammation at the time the sample was collected.

This can be reassuring, but it doesn't mean that every possible cause of symptoms has been ruled out.

A higher result

A raised result suggests that there may be inflammation somewhere in the gastrointestinal tract.

For a child with known IBD, this may indicate that the disease is active.

However, a raised result does not automatically mean an IBD flare.

There are other reasons calprotectin can be elevated, including gastrointestinal infections and other inflammatory conditions.

That's why your child's healthcare team may repeat the test or arrange other investigations.

Why might my child's result change?

Calprotectin can change over time.

If your child's IBD becomes more active, the level may increase.

If treatment reduces inflammation, the level may decrease.

This means your child's doctor may compare their results over time rather than looking at one result in isolation.

For example:

Previous result → current result → symptoms → blood tests → treatment

Together, these pieces of information help create a much clearer picture of how your child's IBD is behaving.

What if my child feels well but their calprotectin is high?

This can happen.

A child can have ongoing bowel inflammation without having many noticeable symptoms.

This is one reason faecal calprotectin can be so useful in IBD monitoring.

If your child's result is higher than expected, their IBD team may want to repeat the test, check other markers of inflammation, review their treatment or investigate further.

Don't make changes to your child's medication based on the calprotectin result alone.

What if my child feels terrible but their calprotectin is normal?

This can happen too.

A normal or low calprotectin result makes significant intestinal inflammation less likely, but it doesn't mean your child's symptoms aren't real.

Tummy pain, diarrhoea, constipation, fatigue and other symptoms can have causes other than active IBD.

Your child's healthcare team can help work out what might be happening.

Can infections affect calprotectin?

Yes.

Faecal calprotectin is a marker of inflammation, not a test specifically for IBD.

A gastrointestinal infection can cause inflammation and increase the calprotectin level.

This is one reason your child's doctor may sometimes arrange stool tests for infections as well.

If your child has recently had a stomach bug, tell their healthcare team, as it may be relevant when interpreting the result.

How often will my child need the test?

There isn't one schedule that applies to every child.

Your child's IBD team may request calprotectin:

• Around the time of diagnosis

• When symptoms change

• During or after a suspected flare

• After starting or changing treatment

• As part of routine monitoring

• When they want to check whether inflammation has settled

The frequency will depend on your child's individual situation.

Is calprotectin the same as a colonoscopy?

No.

A colonoscopy allows doctors to directly look at the bowel lining and, when needed, take small tissue samples for testing.

Faecal calprotectin is a non-invasive stool test that provides information about inflammation.

The two tests answer different questions.

Because calprotectin is much easier and less invasive, it can be particularly useful for monitoring children over time and deciding whether further investigation may be necessary.

What should I do if my child's result is high?

Don't panic.

A high result is information, not a diagnosis of a flare by itself.

Your child's IBD team will interpret the result alongside everything else they know about your child.

They may recommend:

• Repeating the stool test

• Blood tests

• Testing for infection

• Reviewing symptoms

• Reviewing medication

• An appointment with the IBD team

• Further investigations if needed

Don't stop, start or change your child's medication unless their healthcare team tells you to.

Calprotectin is one piece of the puzzle.

Your child's symptoms, growth, examination, blood tests, stool tests and treatment history all matter too.

If you're looking at your child's result and wondering “Is this high?”, the best person to interpret it is your child's IBD team, who know your child's diagnosis and usual results.

And if you're finding the stool collection part difficult or embarrassing, you're definitely not the only family who has been there. It may not be glamorous — but it can be a very useful tool for keeping track of your child's IBD.