Testing for IBD

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TESTING FOR IBD

METHODS FOR TESTING AND MONITORING IBD

NATIONWIDE CHILDRENS: IBD TESTS | WHAT TO EXPECT

The symptoms of IBD are similar to numerous other diseases and conditions, so doctors will use a combination of testing methods to establish a diagnosis. Some of these are then used on an ongoing basis to monitor the disease progression and/or therapy.

Continue reading to find out more about these methods.

BLOOD TESTS

Crohn’s disease and ulcerative colitis cannot be diagnosed through simple blood tests. However, they can still support of the diagnosis and can also be used to monitor the activity of disease and response to treatment. These include blood counts to detect anaemia and infection, liver function tests, potassium levels and vitamin B12.

CALPROTECTIN TEST

By testing a faeces (poo) sample, a test that shows a positive result for calprotectin in the faeces indicates there is inflammation in the gut, which is suggestive of IBD.

COLONOSCOPY

Looking visibly at the intestine with the camera passed through the rectum can help distinguish between UC and Crohn’s for a more accurate diagnosis, or visibly find tumours (cancer) and polyps. Small biopsies can be taken at the same time.

SCANS

X rays, MRI or CT to check for digestive blockages, tumour or enlarged colon.

WHAT IS CALPROTECTIN TESTING?

Calprotectin is an antimicrobial protein that is a biomarker for inflammation.

This protein is expressed (secreted) by some immune cells (white blood cells), especially neutrophils.

During inflammation, neutrophils enter the gut lumen from the blood via a process called transepithelial migration.

When the neutrophils in the gut lumen secrete the Calprotectin protein, it ends up in the faeces.

When there is calprotectin protein in the faeces, this can be detected by testing a faeces sample.

A test that shows a positive result for calprotectin in the faeces indicates there is inflammation in the gut, which is suggestive of IBD.

Image courtesy of Springer: https://link.springer.com/article/10.1007/s00535-016-1182-4/figures/1

WATCH THIS VIDEO ABOUT CALPROTECTIN

CANADIAN DIGESTIVE HEALTH FOUNDATION: FECAL CALPROTECTIN: THE INSIDE STORY ON INFLAMMATION

WHAT IS THE BENEFIT OF CALPROTECTIN TESTING?

Calprotectin detected in a faeces sample tells the doctor there is likely to be inflammation in the gut. It does not tell us what is wrong, but it does tell us there is inflammation:

IT IS A NON SPECIFIC MARKER

It can help to diagnose IBD by confirming inflammation, and rule out NON inflammatory conditions such as:

ï IRRITABLE BOWEL SYNDROME (IBS) ï VIRAL INFECTION

This removes the need to do colonoscopies on patients with a negative result who may have IBS and not IBD. Avoiding the need for this invasive procedure is safer and more convenient for patients, and reduces the impact on valuable healthcare resources.

It is important to know which condition the patient has in order to provide the correct and appropriate treatment.

A calprotectin test is usually done once infection is eliminated and if symptoms continue.

Patients are asked to supply a faecal sample, either in a container provided, or more recently by directly sampling with a small plastic extraction device called CALEX. This is returned to the doctor or hospital laboratory who will perform the analysis to determine if the sample contains calprotectin. This method is: • Simple • Safe • Non-Invasive

Aids diagnosis

Indicates a flare up (relapse)

Can predict a flare (relapse) is imminent - Calprotectin levels will rise before symptoms start

Determines if other tests are required

Monitors how well the patient is responding to treatment

LABORATORY CALPROTECTIN TESTS

Here are some laboratory calprotectin tests you might want to find out more about:

ï Lateral Flow Test ï ELISA ï Turbidimetric test

CALPROTECTIN: LATERAL FLOW TEST

In the laboratory, the faecal sample is prepared in the extraction device and the resulting liquid is applied to the calprotectin lateral flow device.

This works in the same way as the lateral flow test for Coronavirus, it uses antibodies on a membrane to detect and capture the Calprotectin protein.

Alpha Laboratories supplies these lateral flow cassettes.

It also provides laboratories with a machine that can be used to read the results. This is called the ‘Quantum Blue ® ’. Click the thumbnail to watch the Quantum Blue in action.

The instrument reads the ‘intensity’ of the colour on the test line of any positive result.

This enables the laboratory to quantify the amount of that protein in the sample (Quantification). The higher the amount of calprotectin, the brighter the intensity of the test line.

CALPROTECTIN: ELISA TEST

In the laboratory, the faecal sample is prepared and put onto a sample plate.

An ELISA test uses antibodies to detect a specific protein in a liquid sample. It also quantifies the amount of that protein in the sample. This can be used for diagnosis, monitoring and testing.

Alpha Laboratories supplies kits that contain all the reagents required to carry out an ELISA assay for testing of Calprotectin.

It also provides laboratories with an automated machine which will run the ELISA test and read the results. This reads the intensity of colour in the test, enabling the laboratory to

quantify the amount of that protein in the sample (Quantification). The higher the amount of calprotectin, the brighter the intensity of the colour.

CALPROTECTIN: TURBIDIMETRIC TEST

Turbidimetric assays are sensitive tests used to determine the concentration of a specific protein (antigen) in a sample using antibodies.

Alpha Laboratories supplies the BÜHLMANN fCAL ® turbo faecal calprotectin immuno turbidimetric assay kits. These contain all the reagents required to carry out a turbidimetric test for Calprotectin using a faecal sample.

It also provides a machine to measure the results, a BA200 Analyser. However, clinical

laboratories can also run the assays on a number of different instruments that they may already have in their laboratory – it is known as an ‘open source’ assay.

This kit uses antibodies on microscopic beads which will join together and form a complex with any calprotectin protein in the sample. The more calprotectin there is, the more complexes form and the sample becomes more ‘turbid’. The machine passes a beam of light through the sample. It measures the exact amount of light that has come through the sample. The more turbid the sample, the less light is measured. From this measurement, the concentration of calprotectin in the sample can be quantified.

CALPROTECTIN QUANTIFICATION

Calprotectin test results are given as an amount in micrograms per gram of faeces (µg/g).

Elevated: Indicates Some Inflammation

80-160 µg/g

Indicates Inflammation: Possible IBD Disease Flare

Normal

0-80 µg/g

>160 µg/g

Calprotectin Test Result

This concludes the ‘Testing for IBD’ section.

If you haven’t already, read the ‘What is IBD?’ e-book which is available on the bookshelf.

What is IBD?

When you’ve read all three e-books, take a look through the website links that are listed in the ‘Introduction & Resources’ e-book for further reading.

Introduction & Resources